There is absolutely no excuse for any man, hitting a woman, ever, or any individual ever hitting anyone, except in absolute cases of self defense, where their lives, or physical safety, is in danger.
This having been said, my answer to this question is that often times abuse can go from generation to generation. A boy grows up in a family where his father hit him, his siblings, or his mother, and once matured, has his own family, and does the same to them. This can be through learned negative and abusive behavior, unresolved anger at an abusive parent, or for other reasons. It is a learned behavior, and this is what is ingrained in a person. Someone might know it's "wrong" instinctively, but this is what they saw, and, essentially, what was taught to them in their own home.
Beatings can also happen for other reasons, of course, other than learned. It can be about power, control, domination, fear, all those reasons.
This being said, there is no reason to ever beat your spouse, or anyone. We all get angry, as that is human nature. It is more responsible if one finds themself in a situation where violence could potentially happen, or where they could become violent, to leave, go cool off somewhere, and then come back when they are calm, and can make a rational decision about what to do and say, that wont involve violence.
Domestic violence is one issue that I detest perhaps more than any other in the world. Any man, or anyone, who is cowardly enough to do that, should, in my opinion, be locked up with the slime of humanity, and themselves beaten to a pulp in lockup, so THEY can see how it feels to be smacked around. There is no excuse to hit. In any relationship, there are many other ways of dealing with problems, other than resorting to that, in my opinion, lowlife form of behavior.
Mitch