Not denying that if a program coincides with BOTH the regular expenditures you make AND non-accruing payment methods you use - then by all means take the reward. Unless of course, you can clearly see a difference in the selling price that negates the reward.
That is not the case for most credit card users. For example, even a nominally good rewards offer associated with a credit card can be nullified if you carry any balance on that card. Many people are under the false impression that a grace period exists from the date of purchase to the payment due date but, that is only true if you maintain the card with a zero balance. Otherwise, interest is calculated on new purchases from the date of purchase and typically offsets the reward. Imagine the multitude of card users who get a $300 reward check and are completely unaware that they paid $500 in additional interest for the privilege when an alternate payment method would have resulted in REAL savings of $200.
To truly understand the value of a reward it is necessary to include any applied interest, along with any additional unnecessary purchase you made to meet a required minimum. Most card users underestimate the interest (which applies to the total purchase value ) as opposed to the reward which is only a marginal value of that purchase and further exacerbated by any additional purchase made to qualify for the reward.