If vouchers have no value in commerce then why have they existed for so long?

It's like those gas station punch cards for a fountain drink. Every corner store has a 32oz for ¢99. But some people will go out of their way to use one store because they will get that 5th one free. And most likely without even looking at the prices of the rest of goods they purchase.

No successful business operates without marketing. So what are you saying?