How ironic that an Alphabet company, Waymo, only works with a competitor streaming music service, Spotify, and not their own, YouTube Music. I guess that shows how separate they are.
I think it's also a privacy thing; you have to go into the Waymo app and “connect” your YouTube Music account (even though both have the same @gmail.com address), because otherwise the terms of service of one do not allow sharing data with the other without user consent. (Contrary to popular perception Google is very finicky about privacy, at least privacy as defined as conforming to the terms of service.)
That's good news, if I can't use the Youtube Music I've paid for in the Waymo then I'm not going to put up with Spotify Ads instead, better to sit in silence (or use my headphones and my own music)
