You often still want a server somewhere to relay messages. Imagine I type something in my computer at home and turn the device off before leaving the house. Then on the road I pull up the document on my phone. I should see the latest version of the document on my phone. However, there were no moments where both devices were online at the same time.

For this to work, my home computer needs to upload the changes somewhere my phone can access them. For example, a home server or a dumb box in the cloud.

It’s very difficult to make this work without a server kicking around somewhere. So long as the server is fungible (it can easily be replaced for basically any other server), I don’t really see the problem with keeping a server around to relay messages.