yeah, in my experience it tends to be websites that care about ad blockers. youtube is the latest mainstream example but i've ran into some adblock detectors on random backwater sites (although nowadays the firefox + ublock origin combo seems to cut through them with ease). i don't think advertisers really give a crap, for the exact reason you mentioned, but websites do insist on wasting the advertisers' money on people who block ads, because that means they get paid. the real theft is happening between those two parties.

i'm not trying to absolve the advertisers of blame either though. i think the most mad i've ever gotten at them was when i heard how they oppose pay-to-not-get-ads schemes like youtube premium, because it means the most "valuable" users won't see their ads. their endgame is cable, where you pay out your ass for a service and still get ads shoved into your face (where they take up 25% of the time). on top of that, advertisers are a massive force behind the corporate morality sanitization of the internet in the name of "advertiser-friendliness", sometimes in blatantly manipulative ways. for example, don't you dare have a sex-positive attitude because 1) they want to advertise lots of PG-13 shit and don't want it showing up next to higher rated content, and 2) when they advertise more mature stuff they don't want the tits in your content to detract from the tits in their ads.

but yeah, to get back on topic, the anti-adblock technologies are pushed by people who get paid for ads, not by people who pay for ads.