People argue passionately about the importance of staying in control of the content they share here - this has been a key element of the ongoing debates around search and Mastodon/the Fediverse
Meanwhile, ActivityPub works by delivering a copy of everything you say to every server used by at least one of your followers - with no guarantees at all about what those many servers will then do with that data
Here's a more thoughtful related take on this from @timbray https://www.tbray.org/ongoing/When/202x/2022/12/30/Mastodon-Privacy-and-Search