Most science fiction and fantasy authors aren’t interested in writing what used to be called (and may still be called, for all I know) “teen problem novels.” It’s okay, apparently, to have a young adult protagonist who is in some way different, provided that the difference is what the book is about. There has to be angst, and discrimination, and Dealing With Issues† — the non-default protagonist is not allowed to have a story that isn’t all about his or her non-default qualities.
Or, to put it a bit more snarkily, the non-default character is not allowed to enjoy his or her life, or go on adventures, or have fun. If science fiction and fantasy are part of the literature of escape, then readers who are in one way or another not default-normal are constantly being told by the gatekeepers of young adult fiction that freedom is for other people, not for them.
Which is — just in case anybody was in any doubt as to my opinion on the matter — bad.
†Like Dancing With Wolves, only not as much fun.
Dr. Doyle's Blog 
And there you have why I don’t read a lot of YA. I’m not in the market for After School Specials in my pleasure reading.