Last time I was there, they do not have scanners at the parking entrances, so you need the card. As others have said, it is very hit or miss depending on the attendant if they require ID.
It is actually a pet peeve of mine, if we have magic bands that can do a transaction, I am surprised they have not integrated the systems so that they can detect the discount as well. I have to still carry my wallet in order to buy anything so I have my ID and card...but the whole point was to remove those inconveniences.
I suspect it is more to continue to gain revenue from people that don't know they get a discount.