Seems the appeal would be the fuel discounts.

There used to be all sorts of cards that could only be used at gas stations, each chain had their own but they couldn't be used at other chains. Those are gone now as everyone teamed up with Visa or MasterCard and made them a regular general credit card, perhaps with rewards or discounts at that chain but you can use the card anywhere. This Uber card appears to be gas stations only but the MasterCard bit makes it usable everywhere rather than only where they take a fleet type card.