Because it's so bada**.
But also, sometimes running away makes things worse, you have to calculate risk in each individual scenario.
Like, if a bear attacks you, running away seems good, until you realize itself very hard to outrun a bear AND they climb :S
I'd probably punch it in the nose or stab its eye. Apparently, if you stand your ground they might actually back off. (But if you run, run in a zig zac because it'll slow them down a lot to turn)
I don't want to, im vegetarian and don't hurting anything, but I am not being eaten alive if I can avoid it.
I just decided to carry firecrackers on me, lol, because it would startle most people or animals enough to run or get the upper hand.
Oh yes, I've been pinned twice, one I ran away, once I punched and ran. You do what you have to.