To a certain degree, this is all academic. If what dictates your racial mechanics is your subrace, then what race it falls under doesn't really matter. We could have
I agree that making subraces (especially with humans) gets bad and offensive really fast. I really do. In my games and specifically my setting I've gotten around this by essentially getting rid of the subraces in most respects. I have subraces for different continents but that is a biological adaption kind of thing, instead of people from another country over kind of thing. I don't even have drow in my games anymore, but I do have evil elves from a rival kingdom.. that just happen to use the same racial stats as the goodly elves. Or with dark dwarves, I have my own version (I realized years after I wrote them up and used them) that are a twisted almost half-undead variation on the dwarves that PCs play as. I see very little reason to have high, grey, wild and dark -elves running around all over the place and so I cut it. With all of that said, I have no problem with all those variations of elves existing in the main book, I really don't. It doesn't impact me to a great extent. I'll pick the one variation I like and go from there. But I wonder what value there is in collecting unlike races and then calling them subraces of something else. Gnomes aren't a type of halfling anymore than Orcs are a type of Hobgoblin. There may be similarities but they are different races. If we're going to squabble about such things we obviously can't point to real life examples; which is why I would stay away from subracing humans. I just have to try and find value in assigning half-humans into the human category for any real reason. I expect there to be a list, with the elf title coming first then the subrace. I don't expect to see 'Human, half-orc' since that would be confusing and also.. why isn't the half-orc under 'orc'?
This is never going to happen for the very simple reason that pretty much none of the people who are obsessed with needing the Aasimar for symmetry's sake (even though they would be vastly more rare because higher-planar creatures are not into lust or stupid sexual liasons or running away after knocking someone up or the like, so it doesn't even make sense from an "equally common perspective"), don't actually play the bloody beggars, and nor does anyone else, as far as anyone can tell!
I'm not saying they should be added Solely for symmetry sake. I enjoy aasimars, I've played aasimars, I've had aasimars in my games in roughly equal numbers. Heck I even wrote up a civilization of aasimars in my setting (tieflings certainly didn't get that treatment). I think they belong in the book just as much as the tieflings.
Now, on the symmetry bend: just think it is silly to have one without the other. Like having devils in the MM without demons or angels. Just silly to have one but not the others. Like having water gensai but no fire, earth or air. Why do that?
Nah, unlike people who constantly ask for Aasimar, I've actually played them, many times. So I like them just fine, they're probably my fifth or sixth favourite race personally (in their 2E incarnation - their 3.XE one can go to hell for all I care) but I see no need for them for symmetry's sake. I also know that my preferences are not common, and I accept that.
If you like them why aren't you trying to push for their inclusion? It seems like a no brainer to try and at least suggest that your preferred content be included from the get go. If you don't get it then try to see why, but why stop yourself from asking in the first place? Seems a little defeatist.
Anecdote, which I've been told in this thread, is meaningless.
Anecdotes aren't meaningless. They just have to be used appropriately. Anecdotes aren't evidence or an argument. Anecdotes are about as valid as opinion. When people are looking to be convinced of something you try to avoid your opinion and give fact and argument of why something is or should be a certain way. But anecdotes aren't worthless, they inform your stance and that has value so that people can understand. This is just my two cents of course, I'm not everyone and my definition can't be used widely.
As for @
Shemeska 's comments - they pertain to Pathfinder Society and thus aren't just his personal experience but are instead relating to a larger group of people who can play and share results. So, I find fairly significant value in his comments and don't find them anecdotal, though you and others still might.
I know you understand that things take space in books. Not every race can be in there. Something has to be cut. Something less popular. Like Aasimar. As I said, WotC know exactly how many people played Deva in 4E thanks to the DDI, and their extensive market research from 3.XE, they know about how popular Aasimar were in that. They probably don't access to Paizo's PF figures, but I imagine they have a rough idea. They didn't make this decision in a vacuum or without consideration, did they? This is literally a "million dollar enterprise", not a some three-person studio!
Is it your job to make sure things fit into the book? It certainly isn't mine. Even if they go the Pathfinder approach (something I feel is unnecessarily long) they'll add a whopping whole page in length to add another race.
Granted, not every race can be in there. But WotC has seemed interested in catering to as many people as possible, so why not have a conversation like this and see if Aasimar can be one of the few that makes it. If for no other reason than the symmetry thing. But personally, since I like the aasimar more than the tiefling, I feel if they need to cut one they should cut the evil dude since he's evil

and this game is primarily about heroes.
I mean, explain to me why it is you think you know better than WotC and their market research, would you?
The market research was performed when? And what does it tell
them? How do
I get access to
their results (like you seem to have)?
To try and account for discrepencies - in 4e there weren't aasimars yet tieflings are in the PHB. That would automatically make them more popular. And as far as why they would have chosen to do this for the launch of 4e (a decision I assume that cannot be based on 4e market research - on a game that they are building..) well I think that has to do with their design priorities. In the monster manual everything was meant to be an enemy of the party. Tieflings made it as a PC race but no aasimars, evil dragons were basically ALL dragons. Archons, the LG goodly goods, are now evil elementals. And so on, I think it is possible WotC had a bit of a hard on for removing the goodly counterparts to try and un-symmetry the game as much as possible. I don't think it necessarily worked (deva) and I don't see that as a design goal this time either so why not herald the return of aasimars?
I am indeed going by their MM entry, which stayed that way into 3.5E (I just checked - they "usually heed the call to evil", apparently - eff that utter bs!), despite the FRCS. Plus, the FRCS says that enough Tieflings are Evil that the prejudice against them is pretty reasonable, or something to that effect (less extreme than the MM but still, MM 3.5 is AFTER FRCS!), as I recall, which is not the 2E way, nor the 4E one.
"Usually evil" isn't a definitive. Always Evil is. And even then we had non-good celestials and non-evil fiends all over the place. They tend to be more evil than not evil, but given who their parents are I see that as surprising that they aren't more evil. But honestly YES that is a little change. The ability score stuff less so. Considering how much usually gets completely rewritten per edition that is actually VERY minor and yet it is all you seem to be fixated on. So, 3e got it wrong - why not try to correct it for the next edition? Or are you still sore about there being non-weapon proficiencies removed too? Start a pitch (there's theoretically still time) to make sure the aasimars AND the tieflings are both made netural by default. Or whatever their alignment should be.
Unrelated: I sent you a PM the other day - any thoughts?