Supposedly in Western Australia, bells are a legal requirement on a bike. Apparently they can fine you but i've never known anyone that has.

No freakin way am I putting one on mine.

One-hardly anyone has one on theirs & if they do they're a senior
Two-i'll use my voice and say "On your right" or "rider" or biiiiiiiikeeee (if i'm going around a certain corner).
Three-there's no room on my handlebars! GPS, bike light..that's it

Half the freakin time people don't pay attention anyways on some of the bike paths here so why even bother. This is another reason I avoid certain bike paths! I like my detours

I never know if a bell is being rung from behind me or or behind another rider etc.

Same with mtb...I heard "rider" yesterday behind me at our event but it was another rider behind someone else in the distance..