First off it is possible to play D&D (and any other rpg) with little or no actual roleplaying.
Yes, it CAN be done. The game can absolutely be played as a strategic/tactical conflict resolution experience.
However, that is hardly ever done. Mainly because it just is not the expectation, but also because other media do that so much better.
I do think that the problem is not that people are not willing to sit around a table and pretend to be an elf but very very few people are willing to sit at a table and facilitate their buddies to pretend that they are an elf.
I'm quite confident that they don't want to do it in the first place, and in the presence of other people just seals the deal ten times over.
But, they really don't want to do it in the first place.
People equate WOW fans with D&D a lot. (At least D&D playing people). I think that is a pretty big error. The vast majority of WOW fans have background experience in other computer games. No one would presume that playing Halo means the same person probably plays D&D. And no one presumes any roleplay in Halo. WOW is FAR more accurately described as Halo in a fantasy skin than online D&D. Yes, there are huge differences. But it is still played and, more importantly, perceived much more closely to various first person teamwork games.
The bulk of WOW players don't think about their characters thoughts, motivations, roles, whatever. They are playing a game of overcoming challenges. The bulk of D&D players are roleplayers.
It may be that when us tabletop folks start talking WOW, a great deal of our peers are also tabletop gamers. And we bring that legacy along with us and hear our friends talking in the same terms. So we get a skewed view on the experience.
But a typical WOW player has no desire whatsoever to pretend to be a Night Elf. They DO want to use the Night Elf build base for their approach to computer gaming / challenge resolution. They don't even think of the idea of pretending to be a Night Elf.
Again, that isn't to say that there are not a lot of people roleplaying in WOW. They absolutely are there. But they are not representative of the mass scale phenomena that is WOW.