[enriquepablo]

> The password ... is a way of identifying that you are you.

That is not correct. The "system" identifies you by your ID (username - biometrics - whatever). And for the system to ensure that whatever actions you perform on it, are really coming from you, you have to add proof of your identity to the orders for those actions. You use a secret to create that proof of identity. The secret is yours, the identity is the system's (what it uses to identify you).

If you use something you don't treat as a secret (such as your fingerprint) as your proof of identity, you'll be loosing it left and right - you'll be inviting everyone around to impersonate you. Drinking a can of coke and throwing it to the bin would be the same as printing your password in cards and passing them around.