What I Self Host

There seems to be a fad for "self hosting" things now. What I don't understand is: what happened to just having a single device and having it run the code directly and show you the result directly? For example, why can't the thing that connects to the Spotify API just... do that, from a program that runs locally, independent of a web browser, with a GUI created using a standard non-web GUI toolkit? Why would I want to use it by pointing my browser at a machine name (of another device I own) and port number, rather than by launching a dedicated program?

You'll need to port that to windows, linux, Mac, android, and ios for a typical device mix of someone doing self-hosting, and no access from more closed platforms that have a browser.

I can understand Linux programs not being easily made to work on Android, but I can't understand why I'd ever need or want a device that runs Android and a device that runs IOS. Unless they're test devices for development, but I wouldn't be using those to access services in my day-to-day life.