Why are many PTCs all *BUX or BUX*

Singapore
October 15, 2008 5:03pm CST
I first tried my hands on bux.to, but found it to be quite not worth the time and effort, so I decided to stop. Very quickly, more and more PTCs(Pay to click) were springing up, but I notice that most of them still carry the "BUX" name. Why is this so?
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