I pirate everything anyways, why in the hell would I pay for YouTube?
Encourage what you want to see in the world.
You can do that through patronage, if you have the means. Advertising never leads to that. Every sector that depends on large numbers of people contributing a small fraction (like cinema or music) ends up turning into a race to the bottom, as appealing to the lowest common denominator is the most efficient way to succeed. The advertising internet model the epitome of that.
So at least from we see on youtube the ads leads to more niche content, not less. There aren't enough payers to sustain that many niche channels.