Reddit is a prime example of what you're explaining. Reddit has been aggressively expanding their advertising, yet they've done little to nothing to stop ad blockers, or third party Reddit clients, such as Apollo, that automatically strip the website of ads.

I'd posit that Reddit understands that the demographic actually generating content (comments, posts, etc...) are very tech savvy, heavily utilize ad blockers and ad-stripping third party clients. Reddit understands that these users would leave the site en masse if their third party clients or ad blockers were interfered with. This would result in a drop in quality content for "average", non-ad blocking users to interact with, ultimately killing their web traffic and ad revenues.

I'd also bet this is why Reddit has yet to force everyone to the new advertising-optimized redesign, which their power users hate.