That's not the case. Pubky uses Curve25519 keypairs which can be generated from entropy and are even supported by hardware signers such as NitroKey (with secure element) unlike nostr. The Pubky.app homeserver has a toll (either invite code, or SMS, or pay a few SATs) but the homeserver code is open source so you can run your own to connect to the network, which has the advantage of allowing you to host rich media (pics/videos etc.). I imagine that it'll have a nice GUI like start9 or Umbrel or Cloudron at some point in the future. Lmk if you'd like an invite code for a homeserver and I'll send you a insecure & tracked DM on nostr.