People also seem to have a habit of leaving the rubber O ring off as well. How much of a difference that it might make I have no idea, but figured that it was fitted for a reason, so leave it in place.I mostly see it on fat bikes, where the sprocket has been made by the manufacturer to stick out further to help the chain miss the rear tyre. These seem to put a high side load on the sprocket and some definitely become lose. But often, it's caused by fitting the wrong sprocket.