Out of curiosity, what "gross habits" are you referring to that are specific to YA lit and not other categories?
As for NA resurfacing... as an armchair observer, I'm not sure how that would happen if it didn't gain sufficient traction the first time, though I could see why it would be a useful subcategory for some genres, such as romance. (Dealing with one's first "grown-up" romance outside high school, IOW.)
The Gross Habits I refer to are kind of the marketing of YA lit, not really the writing or technique behind it (any issues I find with that, I hold up to all genres in-general, not as a reflection of it being a "YA" thing). It seems that if a story isn't marketed as YA category(which is something that happens on a different level), their core subject matter kinda ignored and the book itself isn't put in the places that might interest/apply to YA audiences. It was only the introduction of the NA category that kind of put these stories about college, adult romance, professional lives, and the reality of things like post-grad and poverty in new adulthood into my forefront and helped me apply my transition with some sort of perspective.
This is highly biased, because I'm basing it off of my experiences in Columbus, OH and how they set up the libraries out there. It's not really the responsibility of the author, but I thought the introduction of the category definitely helped YA readers who were approaching the age horizon to turn around and grab something that applies to the chaos that transition has.
Then again, one could say an avid reader of YA could just search the general Adult sections for things like that. After all, Kindles and ebook readers are more readily available now than they were when I was in high school some five years ago.