One of my psych professors wrote a whole book about geeks and one of the things he comes up with is that America as a whole has an anti-intellectual bias and our culture has "dislike smart people" baked into it. To play D&D well, you have to think. Therefore pop culture hates geeks.

Besides, gayness and transgenderedness and physical disabilities are trendy issues. Being inclusive of them lets the showrunners go "Here, see, we're inclusive! Give us a cookie!" Being inclusive of geeks is not going to get them that benefit, so they don't want it-- I think this proves that they're not so much founded on inclusiveness and underdogs as they've figured out that's a working formula that will get them lots of props from special interests.