I have a working supposition about the lack of genfic, and this is to not denigrate or abuse or look down on anyone who likes or writes gen (I fall in this category as writer), but it's damned hard to truly generate an emotional response based on h/c, whump or infirmary fics. These stories have their proponents, I cheerfully soak them up by the dozens, but to generate even half the angst that a good romance might in a gen story, I have to work four or five times harder to really craft a story that hits people where they live. I have yet to succeed in this, so I'm still working towards that goal!

It can be done, and done well, even in the above mention categories of genfic--but someone who's looking for the rush that a good romance (het or slash, you pick) isn't likely to find it in the average gen story.