Well, you are spending money on those. Each card has a fee. But if you're doing it correctly you should realize far more value than you end up spending.
While I don't deny the possibility that you're right, if you're not involved in the community I'd consider it far more likely that people have already found the most effective manufactured spend techniques.
As an example, CC charge -> Amex GC w/ cashback from rewards site -> Visa GC w/ PIN -> ATM or money order to withdraw is a fairly "simple" MS chain. The convolutions that people have discovered past that get pretty byzantine. But even <1% adds up when you're churning 5 figures.
The lengths of some of the schemes are entertaining in their own right.
