I think opp has a draw here much more often than KJ or 77.

You're not taking into account that our opponent knows what we know. If we make a pot size raise our opponent isn't going to want to shove over the hands such as draws that we want him to shove over. In fact, I don't think we ever get anything worse to call us with a pot sized raise (which makes me think calling the flop is a very plausible play).