I quit Facebook a long time ago. In fact, I was only on it for about a year or so, before I got bored with it. It seemed that it was just another Skinner box - some levers to pull that would engage loud bells and bright lights - something that might amuse a baby for a few moments, at best. It seemed to appeal to our basest instincts - narcissism among them. And they neatly wrapped this up in a package of "social networking" - keeping in touch with friends and families and multinational corporations - so that if you didn't do Facebook, there was something wrong with you.
Scams are highly profitable, which is why people do them. If you can find someone to pay you $100 a month for useless weight-loss products, you can make a fortune. And Facebook's algorithms help you find the sort of people who are susceptible to cons - whether it is weight loss, investments, cryptocurrency, or whatever. The algorithm figures out who clicks and then blasts the same ad to people who have similar profile characteristics.