I think the trouble is that if your a nice guy, if you want that to be attractive - you really have to go all out in terms of dressing real preppy, being a complete straight edge, going almost overboard on being innocent, listening to country and not much else, and finding your dates at church. If your an extreme of something it tends to work well. You've pretty much gotta be something like Toby McGwire in Cider House Rules. Pretty much if you can be that innocent that most other guys don't have much in the way of respect for you - a lot of the real innocent, traditional, and seemingly socially fragile women will eat it up.
Most guys, however like balance - they also want balance in the women they date. They want to be they're true selves, want to be multi-layer, and being all one thing or another seems not only real unhealthy and unless your kind of eccentric in general you have a real hard time even liking yourself minimally when you fit an extrema. That said though, in terms of sexual attraction, it seems like that mechanic works mostly on extrema (at least with women it really seems to go in that direction). As far as the NT guys I've known that seemed to go the longest without girlfriends - they weren't uber geeks, they weren't way out there, in fact they were just too balanced; kinda more like the semi shy guy who listens to a lot of gangster rap, thugs out the way he dresses, and while they were decently successful socially it just seemed like women did less than gravitate to them - part of it I think being just because these guys were nice and didn't fit the stereotype of what they looked like (which, being the stereotype of what you look like outwardly again, that in and of itself seems to be a huge turn on for people - the more you break lines with who people think you should be on first glance the more you seem to get yourself into trouble on that end).