The ringing of the bell hurts a road gremlins ears and they run away. Road gremlins are nasty!! They chased a deer out in front of me. They're also responsible for pot holes, oil slicks, sandy patches and anything else that'll lay the bike down (driver excluded).
So you see, it's just plain good to have one hanging off the bike.
Aaaahhhh that explains it, the gremlins made a pheasant run out in front off me, a wasp get trapped in my helmet (or 2 not sure if it was the same one) and my side panel fall off, and that's just today !!!!