I think it's also because these men actually believe, on a fundamental level, that their wife is their property - that she belongs to them - and so when she crosses him, she must be punished; when her family encourages or helps her to leave, they must be punished because they have, in his mind, stolen from him.
There is, on average, 1 mass shooting a day in the US. How many of these are domestic-violence related? How many of them make news at anything more than a local level? Domestic violence is so common it is almost accepted - not accepted in the sense of, "Well, he has the right," but accepted in the sense of, "Well, these things happen." At the very least, people with domestic violence convictions should not be allowed to purchase guns. But even this is too much for the gun lobby to accept. Through their inaction - or more appropriately, through their actions to ensure that every person, no matter their background, is entitled to own a gun - they, too, are perpetrating this myth that a woman and her body belong to her husband.