The did, but Matrix is coming to reinvent that while but by wasting resources trying to duplicate the state of everything at massive storage costs & without the extensibility because JSON.
The server does matter when it comes to who is collecting all of the metadata, data, attachments. …And having that all that data centralized around a single entity is a problem.
Matrix.org hosts Mozilla’s Matrix server. Further, the way all data is synced to all servers means if someone with a Matrix.org ID joins your room (which is most users), all data is synced to the home server. Almost all of the data is in Matrix.org’s possession & with the servers being as expensive as they are to run, more orgs shutdown when popular causing users to flock to the mother instance.