Not to prevent accidents but to make a mental note to the shooter that he's responsible for his actions....
If a hunter doesn't already have a mental thought that he's responsible for his actions, then he/she isn't much of a hunter to start with and I don't think a number on an arrow is going to change that. Maybe if thier parents raised thier kids properly, they'd learn then that they are responsible for all thier actions, not just while hunting.