Because you can just buy a few domains and create infinite accounts for $10 instead of for free. Doesn't fix anything.
Discussion
Yes it does because you can block them at the relay level by an entire domain then if they spam.
Then they spend $3.99 on another domain and are back in 5 minutes 🤣
That can happen on the Fediverse or anywhere too.
You can block them in 1 minute or less.
There's a qualitative difference between NIP 05 verification and a Fedi server, for multiple reasons. NOSTR relays will accept new content more or less indiscriminately, for one. A Fedi server won't even know a new account exists unless there's already a connection.