You ever see W. Klitschko/Sam Peter I? That's was what Klitschko did in the first eight rounds. And the Klitschko sack slurpers were all over the general form for weeks afterwards praising him for running scared with his back turned from a guy that we now know to be a limited plodder with grossly overrated power.
MMA tend to run away because they need to get back into position. A boxer worries about hands so usually a good cover up can neutralise any attack while you get back in position. In MMA, it could not only result in a punch but also a kick, take down or submission. So yes, it does look like a ***** move BUT its not done for this reason.