> Its best for the remaining people too.

It sure doesn't feel that way to me, as someone who has seen lower-performing (I'd hesitate to label them under-performing, these people simply never should've been hired into the role they were put into in the first place, but those are anecdotes for another time) be PIPed and ultimately let go, because all it means is my own workload is going to go from fucked to even-more-fucked.

I agree. The low performers drag down the rest of the team. Generally, they're not only slow, but the quality of work is poor, requiring constant attention from other team members. Often, the individuals are totally unreliable. They don't respond to messages, won't do PR reviews in a timely manner, resulting in cascading frustrations. You can't give them anything critical or it becomes a blocker...