PIPs are merely an escalation. Ideally yes, there would be communication before you reach that point about expectations, how they're not being met, and how to improve. That's not going to fix every problem though, so you modify your approach as the problem persists. The alternative is to just fire people if more regular, casual communication hasn't done the trick. I think it's more humane to give people clear notice that it hasn't been happening though, and it's either time to really get serious or leave.

I do think it's close-to-analagous to an altimatum in a relationship, though. Sure, there's probably been communication up to that point, but now it's decision time and it's time to get things sorted out or part ways. It's probably headed for parting ways regardless.