Anyone's iPhone 7 randomly asks for your passcode to enable Touch ID? For some reason it happens really sporadically, like once every 2 weeks or something.
That's by design. There are a bunch of scenarios where your passcode is required:
Code:
The device has just been turned on or restarted.
The device has not been unlocked for more than 48 hours.
The passcode has not been used to unlock the device in the last six days and TouchID has not unlocked the device in the last eight hours.
The device has received a remote lock command.
After five unsuccessful attempts to match a fingerprint.
When setting up or enrolling new fingers with Touch ID.
From https://9to5mac.com/2016/05/19/why-does-my-iphone-keep-asking-for-my-passcode/