Both Instacart and DoorDash have benefited from the surging popularity of at-home delivery for groceries and meals. They are betting that at least some of the increased demand will remain after the pandemic ends and hoping that the cards will stoke customer loyalty and attract new users. Banks, for their part, see these new partnerships as a way to diversify beyond travel rewards cards, which fell out of favor with some consumers when the coronavirus pandemic brought travel almost to a standstill.