One scar away from losing access to your ability to pay …
Biometrics can not really be changed. Except maybe through time or trauma (i.e. age or injury). They can be used to uniquely(?) identify a person - except maybe twins - at the expense of anonymity, which has it’s own set of problems.
But because they can not easily be changed they’re a terrible security feature. Once they leak, they’re unusable and you’re hosed. You can’t issue a new palm print for your bank account like you could a new chip card and password.
Also, just because you waved your hand over a scanner does not mean that you approve and consent of the transaction. With tap to pay there were ideas of mobile point of sales devices just tapping on peoples backpacks in a crowded area. You don’t even keep your biometrics markers in your pocket, they’re just out in the open for anyone with a camera. This may be bordering on paranoia, but a few years back (2014) German hackers from Chaos Computer Club took iris scans from Angela Merkel (then Chancellor of Germany) and finger prints of Ursula von der Leyen (then Minister of defense) using nothing but press fotos. Cameras have only gotten better.
TL;DR: Biometrics can be used for identification but should never be used for authorisation.