Because those other options abstract the decision making away from the ‘can never be updated’ part usually into some part of the system where the consequences of a problem/interest in the right solution are also collocated with someone who can do something about it (a API server with ossified clients, or network switch with buggy NIC’s wired into it, etc.)

If truly peer to peer, that is a lot less clear - do you end up in a collaborative p2p document model forking the documents between ‘new rev’ clients and ‘old rev’ clients? Who ‘wins’? What is the consequence of losing?

At least an API server can clearly reject the client and give an error message - if it’s a CRDT, how does that work?