People can still walk while zoomed in though. Not much of an issue in PR, where everyone has an automatic rifle, but when you face mostly rifles + the occasional smg, it is a different story.
Generally speaking, this whole system then looks a lot like a workaround, because it is very unintuitive and inelegant. The prone only solution is limited and not entirely realistic, but it is consistent and works to make the lmgs function in a unique way.