There are other things you can comment on like above, but I there are other ways this can go wrong as well.
I have been diagnosed with bad eczema on my hands recently, and it mostly affects the tips of my fingers. The sensor on my Nexus will now periodically stop accepting my fingerprint scans until I log in with another authentication method and rescan them.
If you don't have any backup ways to provide authentication there are cases where people will get locked out for medical reasons. That won't be extremely common I guess, but fingerprint biometric will, like all systems, not solve all problems.