**For:** If you fall on your head, it will protect it (except for some types of impacts from the side.)

No, this is not an overly simple reply. It's what it's designed for, it's what it does well and it's why you should wear one.

Feel free to edit with documentation about head protection, but I think the number of people on here (myself first) who can say "I fell and my helmet saved my head" are worth any research.