How easy is it to fake a signature for a normal person who has not practiced a person's signature for the intent purpose of faking it? Have you ever tried faking your parents signature to get out of school? I have.
Now the infrastructure required to adequately check signatures is not practical hence it doesn't exist. It's why we moved to pins. Pins are small and 2fa doesn't exist for banks because again it's about the bare minimum and they are out to make money and don't care about customers plus there's government safeguards in place specific to banking.
I will continue to argue that going back in time signatures are infinitely more secure than a 4 digit pin let alone tap but we have traded security for convenience.
Anyways full admit that I'm batshit crazy.
With proper infrastructure yes signatures are extremely secure. But that proper infrastructure doesn't exist.