Matrix is merely federated, right? Why is it unlikely that a situation like email or the Internet will emerge, where the network still ends up massively centralized because that's just more convenient?
Matrix at least seems to have fewer barriers to usability/functionality when self-hosting, which decreases the detriments of self-hosting and slightly lowers the drive to centralize, but until P2P is default standard for clients the convergence is likely to remain with a mostly centralized federation infrastructure target than a heavily decentralized one.
I'm sure some people would disagree with my priorities above but for my experience as a user, that is what makes the most difference to me - not being boxed into what someone else thinks my client should look/act like or being locked into their server. Naturally I think more decentralization is better, but that's more a philosophical preference whereas wanting to run my own server or pick my own client is more about usability and control.
- you can use whatever client/server you want (or host your own)
- you can still communicate with your friends if they're on another server
- servers are run by separate entities in politically distinct regions
None of these things depend on there being a uniform spread of users across servers.
However, just as regular users want to get off the Facebook ecosystem, business's should want to get away from GSuite (Really, it's embarrassing if you are anything close to a google competitor) and I have some optimism there. The "element matrix services" of course isn't political decentralization, but is a helpful stepping stone, and still more isolated per tenant than GSuite (e.g. completely distinct accounts).