Fleeing is a defensive option in some cases, but sometimes it isn't and other times it isn't a compete solution, the violence may be merely delayed. Plus, running usually requires turning your back, which is a risk. And if you're going to run, you best know the territory better than your opponent.

I always laugh when some criminal gets caught in the creek by my house when running from the cops. It happens every few years. They don't know the area and the access, and put themselves at a serious disadvantage in addition to the disadvantage of low ground.