Wouldn't traditional "offline" advertising be even worse?

"We suspect X million people watch this TV show (based on highly inaccurate Nielsen ratings) and then stayed around for the ad break, pay XX dollars."

"XXX people passed by your billboard, XX saw it, X people visited your website and made a purchase, pay XX dollars."

At least that's an independent ranking (I presume?)

Plus you can go watch TV and see that it's actually been on there. Or walk down the street, or pick up a newspaper.

People track conversions - click through URLs contain tracking query params which track the source. If you convert (download a resource, request a demo, start a trial, buy a product) it gets reported back to Facebook.

There's definitely accountability. The problem is that you can't always blame FB or Google because maybe your targeting is off, your ad copy sucks, you dumped the user off the front page of your website and they bailed, etc. There's a lot more to performance and accountability.

If you're only paying for conversions then you should be OK, but paying for clicks is still very common no?