If He can regenerate a whole new head, ya'd think He could do something about His hair!

Maybe he doesn't mind being bald.

Maybe he thinks its sexy, like Kojak? Or the different bald actors?

Maybe he is a Star Trek fan and wants to look like Captain Picard.

Or he could be a neat freak, and wants to look like Mr. Clean!

I think he likes looking like that one butt-hole doctor from ER. The doc everyone hated and was killed when a hellicopter fell off the roof of the hospital on top of him.

The car crash at the beginning that decapitated Betts is a bit questionable IMHO. The stoplight changed and three seconds later a large commercial truck collided with the ambulance, almost entirely collapsing the back-end. There wasnt enough time to accelerate that much from the light change, and if it was already in motion they're on a city street and the emergency lights were on. The truck would have to be both speeding (I'd say around 50 mph in dowtntown pittsburg) and not see the ambulance lights for the crash to happen they way it's presented. Not out if the realm of possibility by any means, just unlikely enough to notice.