Apple has changed the security rules for the operating system iOS. Now iPhone and iPad will be more likely to request a password, although the authorization using the fingerprint scanner Touch ID.
To enhance security, in addition to current requirements, new rule added when the device will prompt you to enter a password instead of using the print: if you haven’t unlocked your device with a password more than six days and using Touch ID in the last eight hours.
These changes appeared in the guide to iOS security, updated may 12, 2016. Note that some users began to notice a change in the behavior of the iPhone in the last few weeks.