If you think it can only happen if you leave the prey item in there for a period of time, you're sadly mistaken. All it takes is one bite to potentially be fatal (either outright or through infection), and that bite can even happen if you're dangling the mouse by the tail. Just because it hasn't happened "in all your years of keeping snakes" doesn't mean it can't. S**t happens. There is next to no reason for us, as responsible keepers, to not do all we can to protect our pets from unnecessary harm.
There is a fine line between a hobby and a mental illness.