The US is not the world, in many countries there was a YouTube subscription without Music. I was even subscribed to it! Here is an article from the largest Dutch website that announced that Google was going to axe that subscription type:
Also, since Youtube Music is just a skin over Youtube, it's not true that your subscription must necessarily be cheaper if there were no Youtube Music.
https://tweakers.net/nieuws/213942/youtube-stopt-met-premium...