Comment by AnthonyMouse

It's the idealist's solution because it benefits the user. Companies typically want to use phone numbers because they're more expensive for users to maintain separate identities with, which helps when you want to track them. Moreover, companies want lock-in to their own network effect, not a federated network that anybody else can permissionlessly join.

It's the sort of thing you get when somebody builds it as a hobby project, or a skunkworks project escapes from a large corporation and is already open source by the time the MBAs get their hands on it. Or, in the old days, DARPA funding.