Martial art sports that use percussive techniques will always have punches to the face. Many participants believe that punching an opponent in the face will give them the advantage they need.
Fact is, however, that the head is a smaller target and easy to get out of harm's way. The amount of body movement necessary to evade a face punch is much less than that needed to move an entire body.
One of the advantages of ducking and slipping is that you stay within range for counterattack while being out of danger for that moment.
For advice on how to perform ducking and slipping techniques you are welcome to email me at firstname.lastname@example.org.