Yeah, I remember thinking along those lines when I first watched Shrek, but I let it slide because they were telling themselves they were writing a kids movie(which it completely wasn't in any mway but they didn't realize that) and could see why they'd be leery of not making them both ogres or both humans.

I thought that too in Shrek 3 and was hoping that it would eventually lead to his getting his act together and stepping up to do what he needed to do, but that didn't seem to be happening(but I was paying less and less attention as it progressed so I can't be sure)