Originally Posted by Raiyn
It's required by law in a lot of places, I have one because it's just better than me yelling at people.
EDIT: Better for them
I took your suggestion a long time ago about putting one on the MTB for off road use. I use it during hunting season to help announce I'm a bike and not a deer. And good for blind corners too. I also think the high pitch of a bell carries a long way better than yelling. People expect a bike almost instantly when they hear a bell, when you yell it takes a second for some people to understand a bike is coming. Lots of practical reasons to have one.