The reason people like idempotency is because it is great for "at least once" systems (as opposed to "exactly once", which is hard to guarantee).

But REST's version of idempotency isn't good for this. If you retry your request multiple times (due to flaky connection or whatever), it only guarantees the same server state if your duplicate requests are bunched up.

For example if you do a DELETE then create it again with a POST, if there is a duplicate straggler DELETE floating around it will end up redeleting your new recreation.