This completely depends on the company. Where I work, PIPs really are designed to give extra structure to the people on them as to what is expected of them and

This completely depends on the company. Where I work, PIPs really are designed to give extra structure to the people on them as to what is expected of them and they're designed to be achievable by the average employee without working extra hours. Of course, they're also private, so you only know someone has been on one if they choose to share that information.