Additionally, because of the internal transfer policy and teams frequently switching out members, a lot of work is designed to be picked up by a new person, especially at the SD1/SD2 levels, so people are generally replaceable. Couple that with the fact that the interview process only tests for academic knowledge, without really proving that you can set up infra and services in production. And even more on top on top of that, Amazon gets a never ending candidate pool. So you get a combination of both poor performance that actually need to get PIPed out mixed in with poor teams that are ran like crap because managers themselves are not really technical and end up not delivering and then having to PIP people out.

That being said, because of this sort of structure, if you know how to make moves and "read the room" so to speak, Amazon is the best company for finding that sweet spot of maximizing revenue/actual hour worked. If you are a talented software engineer, not just a developer and generally know how to navigate around managers, you can hit senior engineer or manager levels quite easily, and then cruise control your way at $300k a year, and with an added benefit of lots of remote positions right now (since wfh is a big selling point in order to not get rejected by good candidates). From talking to people at Google/Facebook, those kind of moves are a lot harder to do.