I'm pretty sure MTV was ad-free when it began. Same with HBO, etc. I'm thinking early 80s. I'm sure not every cable channel was ad-free, but plenty of them were because they got enough revenue from subscriptions.

The thing is, services that start out free can't begin charging users without losing more users than it's worth. But services that start out being paid for can easily find ways to grow revenue by monetizing their user base and selling ads, in addition to maintaining or raising subscription fees. Satellite radio is yet another example.

That's the point. Even services that charge you still might pull this kind of stuff.