Why do some husbands murder their wives rather than seek a divorce?

ABC News is reporting that Brad Cooper, a North Carolina man whose wife was found strangled to death near their home (she had “gone jogging”) has been arrested for her murder.
Another incidence of domestic violence? This follows closely in the heels of the Chicago situation that actress/singer Jennifer Hudson’s family is experiencing with the triple murder of her mother, brother and nephew. There is some speculation that these people were killed by Ms. Hudson’s sister’s husband. There is also specualation that there was a serious domestic violence problem in the marriage, and that the two were discussing divorce.
It is puzzling why someone – if in fact both of these men are guilty of these crimes – would choose to deal with a marriage gone bad in this way, rather than simply seeking a divorce? It is not that difficult to get a divorce.
In New York if both people agree, they can plead constructive abandonment and that will be the end of it in about two months from the date of service of the summons (assuming no children or assets and assuming neither contests anything.)
I am not sure what the situation in North Carolina is. It may be a no fault state like most of the country, making it even easier than it is in New York to end a marriage. Why end someone’s life? It just does not make sense.