A server can do a lot for you that a standalone client can't. It's a machine that's always on, easy to back up, lets users communicate in real time, and the coordination of different client devices per account comes practically for free.

I think one of the reasons federated systems (which once were the backbone of the internet) are being phased out while the huge monoliths like Facebook are winning is that, while people do want a federated alternative, they want this alternative to be philosophically pure in a way that makes the end user experience untenable.

I'm building an open source distributed social network quite similar to this Matrix thing, actually. It's simple, scalable, and it works. It provides a good user experience, too. But fellow geeks tend to hate it. JSON over SSL? Too simplistic. 'We want a VM that runs inside a JavaScript engine which implements its own crypto and _true_ P2P, nothing else will do.'

The trouble is we do know how to make simple and "awkward" solutions work quite well, whereas I have yet to see a "pure" option I'd want to use myself. Of course, that may be personal preference in the end, but I'm kind of hoping I'm not alone.