>Broken bones heal.

I agree with your sentiment about the relative differences between broken bones and head injuries, but this statement isn't completely correct: if you're an adult, a broken bone almost always leaves behind some kind of problem, usually at a minimum the tendency to have arthritis at the point of fracture later on. Broken bones don't heal perfectly, just like significant cuts will always leave a scar in your skin.

Hopefully medical technology will figure out soon how to fix this, and make it so we can regenerate like those animals that regrow tails and limbs, but not yet.