[basica]

I think it depends on the company. Here's two anecdotes for what it's worth:

I worked for a well known defense force contractor and worked under someone who was put on a PIP. The PIP was just a formality in the overall scheme of things as they couldn't fire them without putting them through one first. It was a death march with no chance of success. It was hard hearing them go through it as they were a nice enough person, just not at all suited to the role they were in. In short, PIPs were not seen as methods to actually get an employee back on track in their current role or another one; they were already fired, it's just got a ~12 month notice.

In another organisation a coworker of mine was absolutely useless and were put on a PIP. They genuinely tried to get them back on track and the PIP lasted for a very long time and even renewed their contract when they had a perfect opportunity to let them go. Ultimately they weren't fired directly, when their contract came to its end they put the job up for applications and they didn't win it back. I didn't find out about their PIP until years after the fact and TBH I wish the team knew about it. For all this time we thought they were getting away with their terrible work ethic.