Is there a genre difference between SF/F and mundanefic that would explain this?
There may be. I mean, the Sisterhood books and their ilk make pretty straightforward judgments about teen girls; I have hated such books with a passion ever since I accidentally read a couple of them.
Whereas sf/f, by default, is at a creative remove from such judgments. Even if a series like Warriors was written because they figured it would have a market, it requires a large amount of creativity to pull off believably, and it's about cats--not teen girls.
The fantasy is a healthy one, to use a thought I'm either pulling from Tolkien's Essay on Fairie-Stories or Lewis' book on criticism (I have neither currently to hand). It takes the reader out of their own selfish world for a while and makes them think more broadly than their own desires. Not so some of the more directly marketed "teen" books, which target the same wish-fulfillment niche that romance novels do.