Keyservers are convenient but they're not critical to PGP's functionality. There are other ways to distribute public keys. Actually in general public key server

Keyservers are convenient but they're not critical to PGP's functionality. There are other ways to distribute public keys. Actually in general public key servers are only mildly useful because you can't really trust anything you get from them, you have to use your web of trust of some other way to validate that the key is valid. On the other hand if you wipe (even partially) Bitcoin's blockchain your basically destroy the currency.