Jezza - the stupid adverts pay the hosting bill, the software maintenance etc.
The more people who use ad-blockers, the more the normal advert fees fall. To compensate Google serves the full page, click to dismiss ads every 10 minutes.
Unlike social media (facebook etc.) where you are the product, we don't try a glean info about you and sell it on. The ads are simply that, ads.
The way things are going at the moment, it could come to a paywall or be much limited, which would cost a lot less to run. Or maybe we're just trying to stem the tide of big business and have as much luck as Canute.