I imagine it enables Google to enforce location based licensing for where you can listen to certain songs at a given price point.
Listening to a song in the forest is free, listening to it in a bustling street costs 10¢ per play because you're performing it to people walking by
I would love to have a connected home that did not require _any_ external connectivity or web accounts. Why did I need to login with my Google account and enable location services to set up a Chromecast Audio?