Similarly savings accounts and loans are just messages that describe agreements between private parties.

So how can we have bank regulation, when everything that a bank does is just speech?

The answer is that the law is interested in the content of communications, and whether the messages are cryptographically peer-to-peer this-or-that is irrelevant. If your crypto messaging is about selling drugs or unregistered securities, it's not much of an excuse that you were doing it peer-to-peer.