Because they show ads to people. Do you think they should stop collecting your data just because you block their ads? I don't see why that would make any sense, they have no reason to incentivize ad block use.
But that isn't a fair trade, you argued that your data is worth enough to them that you should be allowed to use their server resources without anything extra from you. But that isn't true, every user like you costs them much more money than they earn.
In such a situation where one part pays for the other parts benefits, you should expect the part that just loses out to try to end the trade. And that is what we see happening here, youtube tries to block you since youtube doesn't want you as a user, since you lose them money.
No, you argued that my data wasn't worth anything. I argued that if it wasn't they wouldn't desperately try and get all my credit, medical, schooling, and browsing history.
What they do is incredibly immoral and despicable. There is no opt-out (even if I pay them money). Even if I never use their services they still try to vacuum up all my data.
Me watching a few YouTube videos a week is a better deal for them than it is for me.
So why are they spying on me when I still pay them? Or are you going to still pretend that hasn't been brought up 3 times now? Or that there is no opt out for their other tracking?