[quote name='skateraXVIII']Not gonna leave you hanging bro, I'm perplexed by this phenomenon also.[/QUOTE]
Many rebate prepaid cards have rather short expiration dates and/or quickly start charging maintenance fees. They also can be difficult to fully use as not everywhere allows split payments. Tough for gas, too, because the pump will try to authorize, generally, far more than is on the card.
An easy way to make sure you use the cards is to convert them to something you know you will use a lot. I like to use them to buy gift cards for a gas station near me--no expiration date and I get a small discount, as well. Also, if I end up with a card with only a few dollars left on it, I'll generally use it to buy an Amazon gift card. Again, no expiration date.