If you had a switch you could turn on that makes your browser send a header that states you use an ad blocker, and that the website could reliably use to decide to show you nothing (including no ads, obviously), would you use it?

If the websites had a similar switch to make it easy for me to decline being tracked, sure. But why should I care about making it "easy for them" if they do not make it easy for me? So that they make more $$$ more easily?