You don’t have to use a model which allows this. Pay-per-placement, for example. You pay a fixed amount to put your ad in a specific article (or on the entire site or in whatever rotation people like) and then there’s no way to rip off advertisers with click farms.
You still need to measure your audience to get advertisers to pay the price, but this is decoupled from the individual ad buys so it can be done differently.
Ha, please have a little trip to any of the open air electronic markets of Eastern Europe(even of those countries that are within the EU) and every other stall has DVDs of almost any PC game/software you can think of. Signs like "newest game releases here!", "Windows 10 all versions no key one dvd!", "Blu-ray movies - 10 per disc!" Are still common. They are not even trying to hide this even though the police are meant to be on a look out for that stuff, but I can guarantee that I could come back with a backpack absolutely full of pirated PC games from one of these markets - that is making people money, no one is doing this out of charity even if prices are low.
> that is making people money
the people buying the pirated software would not have otherwise spent the money on the official/real version. This is the stickler - counting "loss" from this kind of sale is at best immaterial and at worst fraudulent.
For advertising however, you can first of all incur a cost to an advertiser (since costs are calculated per click, view, etc), but furthermore, pirates can even profit from it by having a website and generating fake clicks for that website. If you would not try to prevent this ad fraud you would have bad actors siphoning off complete company advertising budgets to their accounts.