I agree with this, but think that faces face the same issue. If anything, we leave our faces more places than our fingerprints; fingerprints smudge over time, but faces are big enough to capture at sufficient detail using cameras that are already widely deployed. iOS is betrer about facial recognition than Android (and I'm not an Apple fanboi), but it can still be hacked with some patience and enough video frames of the given face at different angles. I would really like biometrics to work, verifiable proof-of-human would be great, but I can only buy into them as an additional requirement for authentication; a piece of privately known/held information is still our most secure authentication mechanism for competent users.