Oddbean new post about login | logout You could say the same of all software. Just because slack doesn't talk to discord doesn't make them members of the same protocol. Interoperability doesn't happen by accident.
Maybe you're arguing that standards can be inferred by published events. Sort of. I think that was always the goal for NIPs. But that's like saying documentation isn't necessary, just go read the source code.
Static documentation isn't necessary, it's true, but it's useful marketing material or a basis for discussion. Nostr has a built-in incentive for people to use other people's events, so that they can capture part of the same audience. An open protocol is a novel idea whose time has come. We're just embracing it.