Adblockers are impacting revenue from a considerable amount of users, otherwise there wouldn't be such messages.
If you want to make an analogy with app stores, visiting a website that's hooked up to an ad network is more like opening the Google Play store, entering a random search, and then clicking install on whatever the first result is. Yes, the web has better sandboxing than Android, but that's still a wild thing for any user to consent to.
When I installed the Play Store on my phone, I wasn't agreeing to give every single app it hosts access to my device. But that's what ad networks essentially force me to do.
Your app store example is a non-sequitur, because users want to download apps. Users in the general case do not specifically want ads.
True, but users want to access content for free, they don't want to pay for every site they visit. And currently it's only possible with ads.
And most users rather bear ads than pay. If everyone uses an adblocker then most sites will either close or become paid.
One visits lots of sites while browsing and paying for each of them is simply not feasible. The solution would be some kind of universal micropayment scheme, but it's unclear how such a sytem could be adopted universally, because making the users setting up multiple micropayment providers in their browsers will not work.