They're just annoying. How is this any different than a bunch of people bringing air horns to a game and just holding the button down for 90mins?
There's no rhythm, musical aspect or anything remotely close to that... they're just dumb.
I don't care if they're banned or not. I just don't see why anybody would bring one to a match. Just seems pointless to me.
What does just making a bunch of noise do for your team? At least with chants you're showing some support or singing encouragement, what does just noise making do? The players don't know if you're making noise for them, for the other team, to protest a call to whatever...
To me it smacks of we have no imagination or intelligence so we're just going to make noise all day.