Why should it? Most ads are toxic. Even if the site is well-intended and doesn't put too many of them, the few ads are still going to track you and disregard your privacy.
If site has ads served from main domain you can't block them
You can block ads with some static files on subdomains/domains, and this drastically change content (like how is image sites looks like without images?)
So, using DNS filtering for big ads providers is OK
For small and smart ads providers will not work
And I mean ads and tracking the same thing. While you can block all kind of "analytics", at the same time you can't block web-server logs with your IP (cookies, etc)