Grand Canyon has been "card preferred" then "no cash" for at least a couple of years. We first saw it at North Rim, where the entrance station is 30 miles from Jacob Lake, which is basically a place with a lodge, and small visitor information center. (It's another 14 miles from the entrance station to the Rim.) So, not exactly a place where banking services are easy to come by. I suspect it's easier for the park service, et al to cope with plastic than cash and change. However, last I knew showers and laundromat at both Rims needed quarters, figure that out.
Many places, the ones that managed to be open anyway, seemed to go to cards preferred or cards only when the pandemic was in full swing.
My husband began buying an annual national park pass back in the late '80s, so it's something we've always done. I've had my permanent senior pass for a while, so we don't usually buy an entrance fee or annual pass. Courtenay will pay the entrance fee for Grand Canyon as part of the fees for his raft trip this year.
They do have machines at the entrances for after/before hours entry, and there is now a machine at Mather Campground for use when they have FCFS campsites. [Usually that is just in the winter, but this year they will have some FCFS sites, as available, most or all of the year, since they are repaving campground loops. Each loop is out of the reservation pool for a set time, but I guess they will release some for FCFS as paving allows.]
This is what's on the website today for entrance fees:
Desert View (East Entrance) and South Entrance Is Open 24/7. Credit cards, Recreation.gov, Your Pass Now, and America the Beautiful passes are accepted for entry. Cash is not accepted at this time. More >
Entrances Fees: Entrance Fees are paid at the entrance stations, or by purchasing a pass in advance from nearby third-party vendors, or online, through Recreation.gov, or YourPassNow. All annual passes are available for purchase at the park's entrance stations.