Comment by darkhelmet

The cynic in me suspects that they probably tried this and discovered that they will lose a percentage of logged-in accounts and how much that costs their revenues/bottom-lines.

Seriously though, even apple does this - where they periodically ask you for your pin/password on phones with fast biometric logins every 1-2 weeks as a memory refresher.

For google: I think they should do a memory refresher too. Once you've confirmed that you remember it, they can stop bugging you for some time. And if a logged-in user can't remember it, then don't log the user out, give them time to save important things.