I think a big compounding problem is the overall prevalence of guns. In most places domestic abusers aren't untrained gun nuts living in a macho wave-your-gun-whenever-you-want culture.

People can obviously do plenty of damage beating each-other with objects, slashing with kitchen knives, or whatever, but guns seem to lead especially often to escalation from shoving to instant death.

When police show up, if someone has a gun everything is a lot more difficult/dangerous.