My impression is that people are on nostr because they want to be decentralization-maxxing. Nostr wears the robes of decentralization and it is not necessary to inspect whether you're using a centralized client (Primal) or a centralized lightning provider (Spark or custodial).

I still suspect Darth is correct. The biggest benefit SN has to offer is pay to post (which I think includes the sybil fee).