The use case people are talking about such as a jealous partner/spouse, or coworker, or only has access to a computer for about 30 seconds while your in the bathroom, does not have enough time to search through all of your gmail or accounts, nor would they want to change your password since then clearly you would know. What they would want to do is see your password, and then later on when there alone they could login to your account on their own computer and casually browse your accounts without your knowledge. Yes Gmail in tiny letters in the footer says if your logged in at two locations but once again this is in regards to non technical users like your parents.