I honestly think this is no different from someone asking where did all the nice guys go, dating-wise.
They're out there. It's just that less people want to read/date them (Welcome to the Friend Zone.). With nice guys, 99% of the time, he will always do the right thing in the end, never say the wrong thing, never lose his temper (unless someone he cares about is hurt), seek to help strangers/friends/anyone, be polite to everyone, will fully express his emotions and desires to a girl so she will understand how he feels about her, and will always want a romantic relationship where he and the girl make sweet love, not sex.
This wholesome character ends up caring too much about everyone but himself and commits selfless act after selfless act, and, to a lot of people, that's boring.
I guess I can understand that. With bad boys, they end up being unpredictable. They can do something assholeish one minute, then do something a little nice later, only to return to asshole mode not too long afterwards. You never know what these guys will do or say (They don't often pick their words carefully), and women love that shit, even if they deny it. Bad boys also go searching for danger and something new, whereas nice guys avoid that stuff (unless someone else is in danger, of course) and stick to regular, everyday routines. And don't get me started on bad boys having a troubled past, and the girl wanting to 'fix' him...