Yeah, because you can easily get a football pool together without the authorities knowing or caring. In a pyramid scheme, sooner or later, you’re going to get caught at it, if you expect it to be at all successful, becuase it depends on recruiting new strangers. Also, if you try to get 10 friends involved, at least one of them is probably smart enough to yell at you for it.
Actually, I’m guessing that the real reason that people don’t bother with them is that it involves giving money to random strangers before getting any reward yourself. Most people aren’t that stupid with their own money. The only way to get lots of people to part with their money is if it has some semblance of legal recognition, or at least some way to make people pay up. Since they’re illegal, this doesn’t really happen, thus leaving them as pathetic spam-mail attempts aimed at those dumb enough to give away money to complete strangers without any hope to get anything in return.