With proper controls, it could be a massive privacy boon. The thing with that physical card is that it has a bunch of information on it that has literally nothing to all whatsoever to its supposed purpose, but can be massive safety and privacy issues. The biggest offender of all, of course, being your address... most likely your residential address.
That bouncer at the club or the bar? He doesn't need to know your address... and should NOT know it. He doesn't need to know if you wear glasses or have a motorcycle or commercial endorsement. There is exactly ONE piece of information that is in any way needed or relevant there: your date of birth. And he doesn't even actually need THAT, just one simple boolean: Are you over 21 or not. So... since NFC is already there... it would be almost trivially easy for Apple to design a system where you walk up to the terminal, tap your phone to the pad, and he gets a little green light if you're over 21, a red light if you're not, and NO OTHER INFORMATION WHATSOEVER... not even your DoB, because that is wholely irrelevant if that value is > 662,256,000 seconds ago.
Same for would-be stalker cops who pull you over. One tap. One light: licensed driver, yes or no. Done and done.
Of course, we know that government will reject any and all sane privacy protections and they'd never land on the Android side in the first place. But yeah... done RIGHT, it really could be a massive safety and privacy win.