Why do some guys look for lose GF but chaste wife?

The male ego. The most some men can take is to have their girlfriend cheat on them, and to make up for that, they are loose themselves, allowing both to cheat. But, they want to "control" the wife, as to the world, he is supposed to be his "wifey", moreover HIS. So, being unable to let their wives cheat on them, as they couldn't handle the rejection, they'd want their wives to be chaste.