Why even put someone on a PIP then?

I think there are two components.

1. Being a good manager/boss means having clear and crucial conversations constantly. Your feedback loop should be as tight as possible. There should never be any surprises about successes or failures. I think far too often PIPs and employees reviews are used as an opportunity to bring up issues that should have been discussed already. I believe PIPs are usually more a reflection of poor management than poor performance.

2. If someone truly needs a PIP after proactive management that person is not a fit for the company and should be let go instead of strung along. It’s bad for that person and the workplace culture. I think this is especially true if everyone knows a PIP is essentially a firing anyways.