The sad thing is, PIPs can exist as much to be a check on managers as to punish employees. PIPs, like annual reviews, should never be surprises. But there are a lot of crappy managers out there[0].
So, yeah, a formal check-in before a firing at the very least gives an employee time to start getting things in order before being completely out of a job, if you disagree with the assessment and don't trust your manager to give you a fair shot, and you can't make the case to the rest of management to give you a shot elsewhere within the company. And that's better than that same manager being able to fire you with zero notice.
[0] and from the opposite side of the desk, it should also be acknowledged that there are also some crappy employees out there who will let their performance degrade to sub-replacement-level.
The trick is to find the places where mid- and upper-management will see a manager using a lot of PIPs as a poor reflection on that manager. Likely they're hiring poorly, motivating poorly, coaching poorly...