Other commenters have already explained it to you. Reviewing existing knowledge on popular topics will often save you time and increase the enjoyment of participating.
So clearly you're here just to call me out, so it's funny you should bring up time saving.
Other commenters on my comment have not provided a good reason. Like I said, I walk through customs and passport control with my phone in my hand all the time (20 or so trips per year) and could easily click this button the instant something unusual happens.