I also don't get why people collect Precious Moments. Or play Cityville/Farmville. Or play most of the games on Xbox/Playstation. They pay good money and time for these distractions. And they come out with "nothing". But they have fun.
There's a lot of people who spend a crap load of time on StackExchange sites. And there's game mechanics roping them into collecting badges and points. But they enjoy it. Do the people answering get much out of it? Virtual points? :) Some virtual pats on the back for an answer well done?
But people enjoy it. Just because I wouldn't spend my money on Cityville or all my time commenting all day on some site, doesn't make them scams.