YA is a marketing segment first and foremost. Sure, there are some authors that buy into it and try to write the kind of thing they think the industry's market

YA is a marketing segment first and foremost. Sure, there are some authors that buy into it and try to write the kind of thing they think the industry's market segment wants. (I'm sure it helps a lot with pitching their books to the publishers). But generally speaking, I think that if a book gets popular with the "wrong" audience, then it's the industry that needs to look into their assumptions, not the audience.