They actually do have an API: https://developer.spotify.com/documentation/web-api/ https://developer.spotify.com/documentation/web-api/ - you don't have direct

They actually do have an API: https://developer.spotify.com/documentation/web-api/ https://developer.spotify.com/documentation/web-api/ - you don't have direct access to the music streams, but you do have access to all the metadata, the various metrics used to generate "radio" etc and the capability to remotely control a Spotify player; so it's perfectly possible to write your own UI / playlist manager / whatever and just treat their player as a dumb part of your audio playback stack.