What difference does it make? If it’s profitable, it’s profitable.
> And are you able to demonstrate definitively that a visitor from FB concluded a sale? If so, how?
Through the variety of existing measurement solutions, or a custom solution.
Twitter: https://business.twitter.com/en/help/campaign-measurement-an...
Facebook: https://developers.facebook.com/docs/facebook-pixel/pixel-wi...
Google: https://support.google.com/adwords/answer/1722054?hl=en
I don’t understand why you seem to think that companies are throwing tens of billions of dollars a year at Facebook (and Google, and Twitter) with not only no returns but also no ability to measure that lack of returns. It’s just such a ridiculous viewpoint to hold.