[_3jh0]

You still need to store that data on somewhere to verify if someone owns a membership and whether it is valid though (memberships can expire).

That data is stored on blockchain vs having a centralized database. Refer to an earlier comment for why having it public is useful.

As for why people didn't use certificates till now, I don't know. I know they use wallet connect more which operates on the same principle but with existing adoption.

[betterunix2]

...why do you have to have a peer-to-peer network managing a blockchain just to verify membership data? It would be simpler to just have whoever controls memberships sign a user's public key to indicate membership (and then you add some metadata for expirations/membership levels/etc.). A user seeking to assert membership presents that certificate and proves knowledge of the private key.

Really though, I am not sure what problem is being solved here. Why do we need this in the first place? What is the attack scenario we are trying to address?