There’s not much personal direct benefit, but if someone cuts you off, honking has the benefit of letting that person know they were being antisocial. Without feedback, it’s easy for people to start to think that selfish behavior is ok.
I think the point is that you will do less to reinforce positive behaviour in others, than you will to amplify your own negative response conditioning.
Though I would add that if you sent your message across in a state of absolute zen then perhaps the reaction would be beneficial all round.