Because most don't value free speech, they value entertainment and convenience more.
Discussion
Let them. Nostr can never win over the mindless-scroll crowd.
It's the most awesome solution for niche communities though. Solve their problems instead, and you'll see users.
Free speech is a weird thing to strive for btw. Literally an oxymoron. Speech is adherence to the vague rules of language (depending on the community you're in), if not it's just brabbling.
Likewise, the most realistic thing we can go for is letting people freely engage with different interoperable communities that each set their own rules without losing that interoperability, making them more like a language.