It requires literally no additional effort to imagine tieflings in Planescape terms than in 4e terms. It takes no effort to disregard all those pictures and recall the ones that I like.
Again, you're claiming that somehow the default effect doesn't apply. That's going to be tough to argue, if you hope to get me to agree with that. It's possible that your insistence that it doesn't apply is at the root of your lack of understanding here.
My concrete example: the original AD&D books told us that dwarves are brown-skinned, yet I have never seen a picture of a brown-skinned dwarf nor encountered any D&D player other than me who defaults to thinking of dwarves as brown-skinned. No effort was required to disregard that so-called "norm".
Was brown skin the default, though?
The first time dwarves were depicted in color in a PHB, the text says they have "ruddy cheeks, dark eyes, and dark hair." That's certainly their depiction in the art.
3e you have a divergence between text and depiction in the PHB (of Tordek), but then you have a consistency between text and description in the MM, which also explicitly calls out mountain dwarves as lighter skinned, so "ah, okay, Tordek's a mountain dwarf," and now you have a better understanding of how dwarves are expected to be played by 3e's designers!
You could go a
long way with the idea that the iconic dwarf in the PHB was white-skinned because game audiences in 2000 were predominantly white and marketing trumped representation there. The implied default of "white" for skin color certainly has a long and tumultuous history. In fact, white dwarves can actually show how hard it is to
change the default.
It's a game of imagination. People will imagine what they want. Did you know that the 4e PHB tells us that, while dwarves "have the same variety of skin, eye, and hair colors as humans, . . . dwarf skin is sometimes gray or sandstone red"? I didn't, until just now when I looked it up. Was there an uproar that this departed from the canon of Gygax's MM and PHB?
...
Also, you still haven't explained why there is no outrage that everything about illithids since 1986 has disregarded the canon established in the DSG.
You'd probably have to ask each individual player, since what matters and what doesn't is subjective, individual, and arbitrary.
If I'd have to offer a hypothesis, I might say that sandstone red dwarves were just an option, so they weren't "default," and that a mid-80's 1e supplement probably doesn't effectively set a "default" for a monster who first appeared in a book 10 years before it.
But you could go with some of the below hypotheses, too.
- Dwarf skin color wasn't very important to very many stories about dwarves
- Other, bigger changes demanded more attention (you don't complain about the rain when you're in the pool)
- Monster changes have fewer ramifications in actual play than PC class/race changes, and so aren't felt as often or as strongly (one character has 24 months to tell us who they are; a monster has about 3 rounds or maybe a night -- comparing Curse of Strahd, again, where the outcry over the changes is greater than it is for, say, the change for lamias).
- More people read and care about what's in each PHB than what's in an old 1e supplement.
- The internet has made codifying and following lore easier, so 2e/3e lore has more norm-setting power in the minds of the fans than previous lore or later lore
- The plot about mind flayers putting out the sun doesn't resonate with the audience as much as the plot about mind flayers being alien overlord for one reason or another. ("I mean, it's got NOTHING to do with eating brains!")
- probably others?
But all this is just brainstorming on why it could possibly be. Maybe all of these have some effect, maybe none of 'em do. Only the affected individuals can tell you why they were affected, and even then they'll probably only tell you AFTER you annoy them. Though if I were WotC, it'd be a question I'd be
super-invested in answering.
The outcry around 4e tieflings is not connected to the "default effect"; it's a distinct response to something which is a flashpoint issue.
(Likewise the response to halflings with cornrows, though the flashpoint issue in that case is different.)
I don't think you've conclusively argued that position, so the authority with which you state it seems entirely unwarranted.