I would also point out that there are adapters to allow bayonets to be affixed to weapons that have full length Picatinny rails that cover the bayonet lug or never had one to begin with as well as bayonets that directly affix to the Picatinny rails themselves. While existence does not prove usefulness (you can get a set of folding eating utensils and a duck call that mount on a Pic rail, after all) there is still a case to be made for the bayonet in real world use and it will likely persist for at least a while longer.