I'll also point out that it takes two to tango and most every internet content company is actively offering free stuff. I suspect one reason that ad-based revenue models are so hard to remove are because eliminating it would require coordinated effort on two separate axes:
1) Consumers would have to coordinate on, "From now on, let's pay for all our services"
AND
2) Companies would have to all agree, "Let's stop providing free product subsidized by ads"
Without some sort of drastic fundamental shift in technology or radical technological invention, I just don't see it happening. Maybe someone makes a killer OS or product that has ad-blocking built-in from the ground up and is also so amazing that everyone switches to it, and so suddenly ad revenue drops to near zero? I guess we can dream.