We need to rethink using biometrics as an authentication method to protect our devices. The problem is that people are lazy and would rather use a fingerprint instead of punching in numbers or letters, which may eat up a few precious seconds of their lives. I've always recommended setting a password to unlock your phone instead of using the fingerprint scanner. The rationale is that you can be compelled to turn over your biometrics, but not knowledge (PIN, password, etc.). We have a recent example of just that when a judge issued a search warrant that gave authorities the power to force occupants of a Los Angeles-area house to unlock devices with their fingerprints.
There was also a case in Virginia Beach, where a judge did the same thing. There have also been cases where a spouse just placed her husband's finger on the TouchID while he was sleeping in order to gain access to his iPhone. Hence the recommendation not to use your fingerprint scanner. It's still your choice, but I would bet people will opt for continued laziness.