We estimate that by 2025, Signal will require approximately $50 million dollars a year to operate—and this is very lean compared to other popular messaging apps that don’t respect your privacy.
Wouldn’t that mean both have to have a connection at the same time? What if one is offline?
You can also just hook up any old phone or computer, install the app, and let it run as the server.
If you have a static IP address, if you want to bother with securing and maintaining it, if you’re willing to deal with downtime when something inevitably breaks, if you’re willing to deal with lost data or also maintaining a backup solution, if… a dozen other things that most people don’t want to deal with.