MMA speaks to everything that people, at least Americans, have grown up with as fighting. Boxing type punches, if you get into trouble just lunge at the guy. It fits right in with how their dad taught them to punch when they were kids, or every fight they have seen in the school yard.
-Furthermore, their skill set is designed for their rules and competition. finger jabs to the eyes, any strikes to the back of the head, etc. are not allowed. So in order for a WC guy to play in their world he/she would have to leave a few things at the door. Whereas if a MMA person would agree to a truly "no holds barred" fight with a WC person I feel that the MMA person would probably bring the same moves, but the WC person would now have their full library to utilize.