A lot of advertisers are still blindly burning money, which incentives various forms of scams.
Sometimes while using a treadmill I play Microsoft solitaire to relieve the boredom. The ads they show there for me are often for 1 individual product (no frequency capping) and if I accidentally miss the close button when I click to close it registers as an ad click, which then forwards to a landing page on an ecommerce site that has an error in the URL, so it loads a 404 error message. I've probably seen that ad thousands of times by now.
Ad ad agency serving the above sort of client has every incentive to buy garbage inventory to pad out their own profit margins.
And publishers that see their own CPMs get clipped by all the scams also have an incentive to run ads on an extended network to bleed advertiser budget.
Almost all the incentive structures lead toward tragedy of the commons.
And as former local monopoly news publishers see their reach & influence decline, they get bought out by private equity in roll up plays, which have every incentive to squeeze blood out of a rock until the brand equity sits right around zero.
