Most payments require at least two factors, e.g. you must be in possession of a card AND know the PIN. Or you must be in possession of a phone AND have it unlocked with your passcode or FaceID, etc. It works well but it’s not perfect.
Biometrics like unique vein patterns give you two factors in one. You must be physically present and alive, otherwise your veins would have no blood flowing and there was nothing to capture and secondly your vein pattern must match the “fingerprint” which is you. That’s much stronger authentication than many other schemes and if it was linked to some sort of payment method and potential even identity service then you could not only pay with your biometric but you could also pay for age restricted goods such as alcohol since it would be physically impossible for someone else to use your hand to buy stuff.
It’s possible for a kid to use your card and pin or phone and passcode though. So there’s the case for biometrics in the future.
EDIT:
Also something like a vein driven biometric would also solve the problem of proving that the person was physically at the point of sale and could hugely reduce disputes and fraud.
There’s loads of value in these new biometrics if they turn out to work well.