Ads are a violation of the sanctity of our minds. They are not entitled to our attention. It's not currency to pay for services with.
Then they have to go to advertisers and say, “advertise on our network where all the wealthier people are not.” A brand like Tiffany’s or Rolex (both huge advertisers) aren’t going to opt into that.
Apart from that, you can bet that YouTube is pricing it in a way that they aren’t losing out compared to ad revenue.
Personally I do like YouTube Music, due to all the user-uploaded content that isn’t available on other platforms.
People who choose that without much thought - because it's barely an expense for them - are definitely tending towards "higher net worth" nationally, let alone globally. A lot of those people just don't realize it, because the entire point of seeking that kind of status is so that they can enter a socioeconomic bubble and not have to care about annoyances (like advertising).