Open web display inventory is a mess. Nearly entirely fraudulent. Every person in the supply chain for open web display inventory, sometimes even including the Chief Marketing Officer of the firm purchasing the ads, is incentivized to turn a blind eye to fraudulent impressions. Fraud is ultimately paid for by shareholders and owners.
This is because everyone in the supply chain is paid per impression, so they don't have any real incentive to root out (or even discover/report) fraud unless the buyer is leaning on them to do so. An unsophisticated firm looking primarily at reach and impressions as key performance indicators sees those KPIs inflated by fraudulent impressions, so even the purchaser isn't really incentivized to discover fraud in those instances. And if you suddenly decide you do care about fraud after not caring about it previously, you're faced with the prospect of having to report to your stakeholders that the metrics you've been giving them have been bullshit for years.
If you're looking at conversions as your key performance indicator then you do care about fraud and will lean on your ad buyer to discover and reduce it, or else just avoid open web display inventory entirely and buy exclusively on platform properties like LinkedIn or Instagram.
There have been various efforts to reduce fraud for a long, long time. Obviously nothing so far has really comprehensively worked. But there are some people in the industry who do make their money and earn their reputations as fraud-fighters, and they continue pushing new solutions. If the fraud problem for open web display inventory could actually be solved it would probably result in a bonanza for anyone positioned to capitalize on a fraud-free supply chain, so some people are incentivized to chase the dream (or at least convince others that they're earnestly chasing the dream).