I'm sure it depends on the company - but really, once someone is put on a PIP, all that's left to do is hammer down the last few nails in the coffin.
My experience? After 6 months of trying (and failing) to even have a simple 1:1 with my direct supervisor, I was told that I would need to meet with her weekly to "get me back on track". I laughed out loud without even thinking about it. When I told them why, they had a pained look on their faces - "well, you need to try".
I turned in my resignation the next day - they were just checking steps off a list and it was 100% the correct decision to get the hell out of there.