Why? Do you laugh at kids who wear bike helmets even if they are on the sidewalk with training wheels? If it reduces a small risk to an even smaller one and there is no harm in doing it, what's the problem? I had a snake who got bit in the head by a live mouse because he didn't quite get his latch/wrap right immediately. In the short second it took him to adjust his grip, he got bitten in the head. I was supervising, but my reaction time is not nearly fast enough for that. He healed fine but it could have been his eye.
In the wild, hunting is dangerous for even apex predators, and in a bin/tank situation, a rat is on a high alert from being moved and dropped into a bin that smells like predator, who has had less time and space to stalk and prepare.
999 times out of 1000 sounds minuscule but when you think of how many snakes we collectively have and how many of those are fed on a daily basis, that amounts to a lot of bitten snakes.