Because the people that are actually building really cool and interesting stuff are not the people that are typically supported by the VC bros that have tried to basically remake legacy social media by turning a protocol into a platform which is totally not the same thing.
I don't particularly care that much about Nostr in the long run because it should just fade into the background like how everything is networked because that's the entire point. It's what is built on top of a (hopefully) stable protocol that is flexible and irresistibly unstoppable that matters.
"Joining Nostr" is fiat thinking. Building on the freedom protocol is not.