I might not use matrix.org, but when 90% of my friends do (and currently that's closer to 100%), that doesn't do much for me...
(But also: I don't have the resources to run a separate instance for myself, let alone for my friends.)
(But also: I don't have the resources to run a separate instance for myself, let alone for my friends.)
Meanwhile you also have the option to get a client with multi-account support. Again, not all clients have this, but this is again something that no other messenger does, or will ever allow purely for market reasons.
Hint: the correct answer to this is not "Well there's your problem you're expecting to run it on Digital oc-" no, this attitude helps nobody. Like Picard said, make it so.