You can set a default credit card, no need to confirm which one.
Either way, I think we can agree that FaceID is a nice addition to iPhone, and removing TouchID is a step backwards. They'd complement each other nicely.
If I only wanted to use a default card, it would be no issue. As I have 4 cards, and use them about equally, there's just a 25% chance that I'll have the card I want when pulling out my phone, 75% probability that I'll have to override. Default is therefore virtually meaningless. "Last card used" would work just as well (or poorly) in my case.
I think we
can agree that Face ID is likely to be a nice addition.
At this time, when we're all speaking hypothetically, I can't agree that removing Touch ID would be a step backwards. To me, "step backwards" would mean that Face ID would not be as useful or effective as Touch ID. That would depend entirely on implementation, of course. Since I'm obviously optimistic about that implementation, I can't agree with you at this time. Maybe after experiencing Face ID in person I'll have to change my mind.
If Apple had to provide two systems for ID, I'd consider
that to be a step backwards. I find that kind of redundancy to be offensive - increased cost and complexity for, presumably, little additional benefit (eg. sometimes Facial ID may be superior, sometimes Touch ID may be superior, most of the time either will do quite nicely). Either a system of this sort works well enough to stand on its own merits, or it doesn't.
Maybe the skepticism is driven, in part, by the progression of rumors. Initially, the rumors favored Touch ID built into the display, with rumors of Facial ID coming much later. A person might get the impression that Facial ID is some sort of half-baked stopgap because the display-embedded Touch ID didn't work out. Maybe that is how things happened, but I see things differently. A well-implemented facial recognition system cannot be rushed into production, and a display-embedded touch sensor is very hard thing to do - resolution has to be much greater than the normal touchscreen sensing grid. Both would have to be in active R&D for quite some time. In an organization as large as Apple's, both those systems, and perhaps others, would have been in development on parallel, competitive paths. The decision as to whether to pursue in-screen Touch ID or Facial ID could have been made two years ago, or more, or they could have kept both in development for a while longer, with one as a backup for the other.
From my perspective, you just have to look at AR Kit to understand that 3D Facial ID was deemed ready for prime time a while ago. AR Kit is one of the foundation technologies for effective 3D Facial ID, and all indications from developers is that AR Kit is very, very capable. Further, since the front camera could not be eliminated (what, kill selfies and FaceTime???) and an infrared 3D sensor is quite small compared to the Home button (and can be co-located with the front camera), and the secure enclave and other elements needed to support the back end of the process were already in place (the difference between storing/comparing facial measurements vs. fingerprint measurements is negligible)... Add in the added functional and security benefits of effective 3D facial recognition, and you have what, to me, is a no-brainer: Pie in the sky to embed a Touch ID capability in the display vs. a superior system built from standard components.
[Added: Further, it's much easier to implement secure 3D Facial ID into iMacs than to implement secure Touch ID in an external keyboard. When you consider that 3D sensing will be necessary if hand gestures are to be added to Mac computing... 3D recognition systems of some sort were likely
always the favored solution for Macs.]
When the vast majority of the press, Wall St. analysts, and Apple fans were thinking, "What are they going to do about Touch ID if the Home button goes away," the unvoiced assumption was that iPhone X would
have to have Touch ID. I think that was a failure of imagination. Nobody thought Apple might "creatively destroy" Touch ID so few years after it was introduced.
People's assessment of the likely weaknesses of 3D Facial ID are eerily similar to their assessment of the likely weaknesses of Touch ID - in both cases, they're colored by the poor quality of existing implementations. Yet Apple's "thing" is to get things right, rather than push a half-assed product onto the market. That's why Maps was judged so harshly when released - it was so atypical of Apple. I have a (strong) feeling that 3D Facial ID will be another case of Apple at its best, rather than its worst.