Because most people become overcome with fear, and those not scared to near death are enraged. Few can remain rational in such circumstances.
My closest experience was an enraged 300 lb sow pig which came over the fence while I was castrating her babies. She hit me in the chest and knocked me straight down onto my back. There I was with 300 lb of pig straddling me trying to eat my face and throat.
I very consciously shoved my left arm in her mouth to protect my face. I was wearing a heavy down coat, which got torn to shreds. But I only suffered a few minor scratches before one of the baby pigs came running past and momma pig decided she was more interested in chasing down the baby than in eating me.
Also, Roger can tell us about the damaged caused by letting a big dog get even a bit of your hand in his mouth. It is hard to get a good grip on anything when the bones in your fingers have been crushed to smithereens.
Quick summary: pit turned on his owner, mangled his paws, broke off attack and next day was hauled away by CC animal control and given the pink fluid ticket to the happy barrio in the sky. Gotta' love a sweet ending...
