I guess you could say adult is part time for me. I do both adult and mainstream, but they kind of merge together. I'm in the business of getting web site visitors and selling them something. If I get money from pokemon traffic, or adult traffic it's still making money off website visitors.
There's probably such a big emphasis on adult because it's a major chunk of web traffic as a whole. It's the oldest industry in the world and isn't going anywhere.
Adult is also the easiest targetted traffic to get.
