The World Wide Web is already a (social) network, and URLs serve as profile identifiers. But the WWW has walls which wall off private territory. That's a good thing.
The few things that require internet wide publication are actually the worst parts of the internet. For example, Certificate Authorities and DNS.
Another example is Bitcoin. People want to be more anonymous on the blockchain. They don't want to publish their profiles there.
Another example is China's government social rank system. Surely you don't want *that*.
Decentralized Social Networks in the sense of Facebook would never happen in a free country, and they are not desirable.
Furthermore, the whole ideological quest to penalize private companies like Facebook for using customer's data for marketing is misguided.