There's another factor: MMA fights are one-on-one in a controlled environment. If you get into a fight in a bar and take your opponent to the ground, his friend is going to kick you in the head and now you have a concussion. MMA fights and the styles that succeed most frequently in MMA are based around this kind of maneuver, and it works because you know you are fighting one dude and nobody else is going to bother you.