We pay $179 a year for Amazon music. We use Alexa all the time to play music. How is that not a huge revenue success? It sounds like they are not properly factoring that in as a downstream impact.
It takes a LOT of $179/year subscriptions to pay the salaries of 10,000 engineers. Especially since a lot of that subscription revenue for music will go to licensing the content.
In general music is a business you go into if you want to lose money. At Amazon's size they can probably negotiate better deals than smaller companies can, but it's still a painful business to be in.
For $168/year you could get YouTube Premium, which comes with YouTube music and ad-free YouTube (not counting ads inside the videos done by the content creator).
Or as part of an Apple deal that comes with other stuff you may want. The music subscriptions are all pretty much the same unless you have very niche requirements.