Most relays don't respect expiration tags, and hardly any clients add them. Many relays ignore deletes or are sloppy about them, and the public relays are usually completely obsessed with archiving every 👍🏻❤️🤪⚡ anyone ever posted ever. Most normal users assume more "monumental" events like longform articles or publications/books will be maintained, at least in the medium-term, so they put The Important Stuff in them. They don't usually realize that ABSOLUTELY EVERYTHING is being logged, catalogued, and archived, so that it can get dug back up in 10 years, to get thrown in their face. As soon as they realize this, and notice that no client has a delete button, they head for the exit. Universal event persistence is a protocol bug, not a feature.

The problem is that with the exception of cases where you only post your notes on private relays, where there isn't much reach by definition, there's no way to guarantee the note won't be broadcast somewhere else and stored till time immemorial