It's illegal to run without one, not that I care, mine works about half the time. I also ride high every time. Nope, still haven't had any close calls with any drive-thrus and children in the way.
I like a horn when riding with someone else, so I can honk if I pull over, or have to get one's attention for some reason. When I come up on a car-load of females and they have a bumper sticker that says, "Honk if you're Horny" I'd be sad if my horn was sitting in some parts bin.