Because that's the overwhelming percentage of users: bitcoiners and people working on Nostr ecosystem...
The problem comes from the lack of the others not from the ones already here, they're just being themselves.
Discussion
That's certainly a good point, but which normie is going to care, to join?
IMO social media decentralization is not a big enough incentive, most people don't care about that, not even most bitcoiners.
But money is. They will care about that. In due time...
And yes. More most people are needed. Probably next big wave will be when twitter becomes a paid for all app.
People look for content they care about.
Nostr = Bitcoin/Nostr echo-chamber
Mastodon = Not Bitcoin/Nostr echo-chamber
Tech aside, seems like people would be joining Mastodon.