This is reasonable. However, I don't like being forced to also pay for their music streaming service because I already pay for (and prefer) a different service.
If you watch a lot of youtube video's it's worth it for just the ad-free experience alone. I actually did some math a while back and figured out based on my hourly bill rate that it's technically costing me money to not pay for YT premium (that is the time spent watching ads times my bill rate was greater than the monthly subscription cost).
If I only watched YT on the browser sure. But I mainly get it so I can go without ads on mobile and on my TV. Yes I know there are apps like Vanced but I personally find it worth it not have to always look for workarounds.
I don't care about YouTube getting paid, but apparently YT Premium is lucrative for the creators (in comparison to ads). It's a very cheap way to support the people who make the content that you enjoy.
You're not really, it just doesn't cost YouTube any more in terms of licensing the music for their music streaming service than it does to clear the rights for YouTube Premium, so they literally may as well include it.
A YouTube Premium lite is available in a few territories, but where it isn't that's because the music situation means it could cost single cents a month less than the full service and therefore isn't worth doing.