Earlier quoted context omitted.
Consider setting up a pihole locally or on a vps.
This isn't that effective anymore. A lot of sites now proxy their ads through their own Web server for the express purpose of making them harder to block. The only way to effectively block these, without something horribly draconian like breaking TLS, is a browser extension.
This doesn't mean what you think it means. What you wrote means that web sites put text on their pages stating, "We're proxying our ads so you can't block them, nanny nanny boo boo!"
You probably mean "specific" purpose.
More to the point, this isn't new. We were doing this on web sites at least as far back as the early 2000's.