Understandable actually. Server maintenance costs money and if a 3rd party chat app; which significantly has more usage than other forms of social media; is trying to connect to the server, they have to handle that traffic too. Remember, it is not just about data size, but also the sheer volume of connection to handle.
I think the solution is just P2P with each peer acting as a relay to the other too. The protocol needs to be designed in such a way that no-one in the middle can reply to send false acknowledgement so as to prevent sybil attack or other attack where a malicious actor is a part of the network.
I mean systemd didn't force any distro to use their software nor force any other developer to assume systemd is present. Any software that assumes systemd is present is not the fault of systemd itself, in fact I'd argue it is a sign of its success. Argue all you want about systemd being monolithic and single point of failure, at the end of the day, software dev needs some tools, and if systemd already provides it but other software doesn't, of course they will choose systemd.