I think the reason that stops the competition from directly doing it is because if the target proves that the accusations isn't true then there's a potential backfire from them which might damage their company. And I think they all have some tacit agreement that they will screw each other in a legal way because that's much satisfying than the dirty one.
But if the accusation has strong evidence then it certainly will not backfire, because the possibility that happened is cheating on the promotion he made. They make efforts from time to time to improve reputation but unfortunately, there are some of them who spoil it with their own actions and of course that case will be very unfortunate because after all the reputation will increase depending on the services they have.