* Some % of people install adblockers, but that number doesn't grow that much.
* There are more people being reached by advertising than ever before. 7.7 billion people in the world & still only about half are online. So overall the number of users they're reaching is growing even if they lose some to adblockers.
* You currently have to install an adblocker per device or even application (unless you are in the minority putting it on your router at home). This means that adblock rates vary and a user installing an adblock somewhere doesn't mean that user is globally lost from advertising reaching them somehow.
* There are multiple modalities for ad networks (app, web pages, etc etc). Google is involved in all of them. Ad blocking has variable performance across those networks unless you really know what you're doing (e.g. in-app advertising is very hard to block on iOS).
* The price of ads can vary driving up revenues. Not all ads are priced equivalently so Google can drive value that way by making the ads more valuable to advertisers or making more expensive ads more appealing.
* Inflation will naturally increase total dollar amounts even if everything else remained constant.