They weren't popular enough to get added because very few major things like races and classes get added to the core. But by now, you should realize that far fewer core things ever get taken out. Binders and warlords/marshals were never core in 3x (I've heard of the classes; I have no idea what books they're from), and WotC chucked a lot of things from 4e on principle. Even artificers didn't make it to the core and they're quite popular.
Which is why halflings won't be taken out. Instead, other races will get added in. You might just have to carry a thicker book. Or hopefully 6e will be more digital-friendly so you can leave the heavy book at home when you go elsewhere to play.
Warlords were core in 4e. So, yes, things get taken out of core.
Binders? Sure, they got mugged by warlocks. I understand that.
So if we were to take your logic we'd eliminate every single race up to and including dwarves and leave just the big five? (Dwarves haven't been bigger than tieflings and dragonborn for years)
I'm sorry, I thought this was a thread about halflings. All this "Well Whaddabout" stuff is just smoke and mirrors.
Halflings are not the least popular race in the PHB - that would be gnomes. They don't seem to be the second least popular race in the PHB - that would be half-orcs (although it's close). And if we're eliminating races on the grounds of being a long way from humans then I see absolutely no reason to put the scalpel between halflings and dwarves that doesn't amount to cherry picking.
Again, thread about halflings. I have zero problems with 6e saying, "Whelp, we tried with these races, but, they don't really get played, and they don't really add anything to the game BECAUSE they aren't getting played. Let's try something new". You seem to think that because I would cut halfings and send them to the Monster Manual that I wouldn't do it for other races. It's not an either/or situation. I have zero problems applying the logic to anything in the game.
You guys are the ones trying to paint this as, "Well, you just don't like halflings, that why you want them gone". It's getting rather tiresome being accused of a bunch of stuff that really isn't germane to the point.
And if you have no opinion about halflings why are you even bothering to post?
Sigh. Context matters. You and others keep trying to paint this as a bunch of "halfling haters" trying to boot halflings. In my case, nothing could be further from the truth. I've been accused repeatedly of hating halfllings. I honestly could not care less if halflings are in the game or not because they play virtually no role at my table. In the past ten years, I've seen maybe one halfling character. Removing halfings from the game would have zero impact. But, I don't want them removed. I recognize that some people (a TINY minority - 95% of people DON'T) play them, so, move them over to the Monster Manual with playable stats, same as a bunch of other races that aren't really popular enough to get put in the PHB, but, people still play them.
Then, we'll add some races that actually gain traction. All I know is, keeping the same races in the PHB has meant that the PHB becomes less and less relevant as the edition continues. My current group is playing exactly one (Tiefling) PHB race character out of 5 PC's. No, I'm sorry, I tell a lie. We just added a Dragonborn character after losing the half-orc character's player to real life stuff.
It would be really, really interesting to see how these numbers track over time. I wish we could see that. Hey, maybe I'm totally off base here and some races are far more popular than they seem to be. That could easily possibly be. OTOH, it could just as easily be that various races have been buried under the veritable tsunami of new players out there that have joined the hobby in the past five years.