A 1080p music video costs about one tenth of one cent to serve to one person at retail CDN rates.
You could easily host this yourself and decide what the terms are to view it. E.g. ads, or paywall or free because you benefit from the exposure.
Once upon a time AdSense/YouTube saved you from getting an unmanageable $5,000 bill from your ISP because your content went viral but nowadays their value proposition is more about network effects plus built-in revshare scheme.
Maybe if they paid their users more, so they didn't also have to add 'sponsor segments' inside their video's it would make more sense. The bundling music for the same price is the same crap cable and phone companies have been doing for decades, that most people hate. Let me buy just youtube without ads, and keep spotify.
But as it sits right now, $14/month for video's without youtube ads, but still with ads added by the creators themselves (or paid promotion, I guess) is pretty expensive, compared to $17/month for actual movies with no ads at all.