Also, why using fingerprint to unlock devices is not recommended?
(Once more for the folks in the back: fingerprints are usernames. Passwords are things you can rotate.)
Of course in places without something like the 5th, and you lie a few times, your death may find you quite quickly, there is at the very least an option... With a fingerprint, no options. Have a picture of your finger and game over.
Your fingerprint is an attribute of you and has no such protection.