This is probably a pet peeve because I used to be guilty of it myself. In much of my early writing, having a character be popular and concerned with boys and makeup (one of the YA default versions of "normal") was a shorthand way in my work of indicating that character was in some way awful, not to be liked or trusted. At some point, though, I realized that not only was this hugely cliched, it was also not an accurate reflection of how the larger world works.
I'm not sure how exactly I realized this, though I can think of several influences. One was writing a short story called "Alien Promises," in which two very different girls discover they're both waiting for the aliens to come and take them away. While one of those girls is the sort of reading-obsessed loner you'd expect to be waiting for aliens, the other turns out to be a more normal sort of kid. Except that she never thought of herself as normal; she had her own story, which made her as unique in her mind as the bookish kid was in hers.
Another, earlier influence: there was a kid I knew in college, who was likeable enough, but who also seemed terribly normal to me. He clearly wasn't one of "my" people--not a bit of bookishness or fannishness about him. Yet one day he surprised me; he started telling me about this story he'd been writing. It was a boring story, it wasn't my sort of story, but that didn't impress me so much as realizing that he told himself stories just like I did. And that those stories clearly meant as much to him as mine did to me. I used to think only a select few quirky people actually had stories inside them. But listening to this guy, I began to understand that in fact I had no idea who had stories or art inside them and who didn't; that wasn't something you could tell just by looking at a person and their life, just by looking at the surface details.
And then there was this fantasy novel that I read, also in college, that I might otherwise have liked, except for this: everyone gave the one normal character in the book's group of friends a hard time--even though she was perfectly nice, perfectly kind--for no other reason than that she was normal. She was scorned for surface things, like being fond of tennis, or not having read the right books. And the worst part was, she kept hanging around with the people who scorned her, even though she clearly deserved better, because somehow hanging out with the cool quirky artsy folks was better than finding her own tribe, a place where she might have actually fit. Even though I had read the right books (and was not fond of tennis), the injustice of it angered me.
I understand the appeal of wanting to believe that those of us who are outsiders, or somehow on the fringes, will one day be rewarded; I spent enough of my own childhood and adolescence waiting for that to happen. But if all we do once we find our tribe is exclude and scorn those outside of it in turn, then what have we learned? What was the point of our spending all those years struggling with being outsiders in the first place?
Anyway, the point is--for me at least--that everyone has their own story, and that even people who seem normal and mundane mostly believe themselves worthy of magic, in one way or another. And if a story limits magic--or any other marker of specialness--to only a certain group of people, there ought to at least be some good reason for it.