This used to come up a lot in meta-fedi talk on Mastodon. The general feeling (from my own observation) is that a central authority for user accounts would defeat one of the big advantages of decentralization: that one service going down does not bring the rest of the network down with it. If all logins have to authenticate to a central service, then if that service is offline then nobody can log in anywhere.
There is capability for federated login in ActivityPub, though, it just doesn’t seem to be very widely adopted. Pixelfed has a “sign in with Mastodon” login option, where you can use your login on a Mastodon instance to authenticate to Pixelfed, and then presumably you can use Pixelfed with your Mastodon account instead of having a separate Pixelfed account. My masto instance doesn’t seem to support it so I don’t know what it looks like.
This used to come up a lot in meta-fedi talk on Mastodon. The general feeling (from my own observation) is that a central authority for user accounts would defeat one of the big advantages of decentralization: that one service going down does not bring the rest of the network down with it. If all logins have to authenticate to a central service, then if that service is offline then nobody can log in anywhere.
There is capability for federated login in ActivityPub, though, it just doesn’t seem to be very widely adopted. Pixelfed has a “sign in with Mastodon” login option, where you can use your login on a Mastodon instance to authenticate to Pixelfed, and then presumably you can use Pixelfed with your Mastodon account instead of having a separate Pixelfed account. My masto instance doesn’t seem to support it so I don’t know what it looks like.