I think it's "the algorithm", people basically just want to be force-fed "content" – look how successful TikTok is, largely because it has an algorithm that very quickly narrows down user habits and provides endless distraction.

Mastodon and fediverse alternatives by comparison have very simple feeds and ways to surface content, it simply doesn't "hook" people the same way, and that's competition.

On one hand we should probably be doing away with "the algorithm" for reasons not enumerated here for brevity, but on the other hand maybe the fediverse should build something to accommodate this demand, otherwise the non-fedi sites will.