To give one legitimate use: One of the clients I work with is a university. Staff are forced to set-up 2FA. We received numerous support calls, particularly f

To give one legitimate use: One of the clients I work with is a university. Staff are forced to set-up 2FA. We received numerous support calls, particularly from users of Safari, who would find themselves accidentally in incognito/private browsing mode - and then complain that the "remember my device" functionality (which relies on a cookie) didn't work. We solved this with a visible warning to users who are in incognito mode to remind them that they will need to provide a new code each time they login.