It's not that Kevin doesn't want to bottom its a very important and personal thing to him, he only wants to bottom to a person he loves. In fact he does in season 2 i believe it is.
I love re-watching it, and I don't do that with too many shows. Definitely worth buying the DVDs. I love the last scene of the last episode. But then again I'm all about Bro (I'm a sucker for bad boys), and Bro/Kevin.