I agree. They definitely go hand in hand. SN, for example, would have a ton of new users if everyone became a bitcoiner tomorrow. At the same time, SN is creating more bitcoiners. 

You can actually think about it the other way around: what if there were a great service payable only in Bitcoin? Necessity drives adoption. You probably didn't get Internet access or a computer for the sake of it, but because of things that were only available through those.

AskSN

What would it take for a decentralized pay-to-download platform to exist?

Honestly, there's so many projects like this that could be put into place right now if bitcoin adoption were higher. 

What it would take is for all of the bitcoiners to continue the long and slow process of orange pilling the world. People are resistant to change, and bitcoin isn't a simple concept. 