The point is that fingerprints may not mean the administrator of the device is present, in the same way that a password that cannot be changed also may not mean the administrator of the device has authorized an action. Fingerprints are useful in cases where the effort of copying a fingerprint is greater than the value of the target. They’re great for almost everyone with low value systems, like your average easily pickable front door lock. They’re good for keeping honest people honest.
Fingerprints are a problem for high value systems. - HN

see also

• German minister photo fingerprint ‘theft’ seemed far too EASY