It all boils down to the tradeoff between convenience and security. I don't think it is particularly easy to replicate a living hand with all the blood vessels. And it is not particularly easy to get a NFC ring with a secure element compatible with payment terminals.

I thought that the engineering team at Amazon did a great job with Amazon One. I wish someone could pick up the tech and carry on.

Yeah 25 years ago people said stuff like that about fingerprint scanners, and then they got hacked by literal gummy bears:

https://www.theregister.com/2002/05/16/gummi_bears_defeat_fi...

For 2020's-era palm scanners you don't have to replicate a 3D hand -- just like a video chat doesn't replicate my 3D face. You just have to emit photons (some of them infrared, yes) in the correct pattern. The hack won't look like a 3D-printed hand, it'll look like a display panel that works beyond visible wavelengths. It'll probably be some device developed for a totally unrelated market, and then one day "whoops, all those palm scanners are 0wn3d" (natürlich auf Deutsch) will be a talk title at CCC.

But all this is academic. The real problem with biometrics is that when your password is a body part, you can't change your password.