I was put on a PIP very shortly before landing a (mandatory, due to my country's laws) nice fat severance package. I suspect* the hope was that I would have been offended by the PIP and found new employment, saving them the severance.

* there were also noises being made about upcoming mandatory night/weekend support rotas; in hindsight it seems awfully like those of us who were expensive were being oh-so-subtly encouraged to move along under our own steam.