While OIDC essentially makes sure that we aren't rolling our own auth solution, making things like passkey support, 2FA and permission scoping super easy, SCIM allows for polycu- uh, I mean organizations cough to automatically provision polyproto identities for critters!
To explain why SCIM is cool: imagine being invited to your polycul-organizations' self-hosted services network, and immediately having just one account and sign-in with which you can use their @polyphonychat instance, the shared media library, music server and fedi instance, without having to do anything extra!