It's a good reminder of what resolution you're using. Let's say you've chosen to shoot a few photos at a lower resolution the other day to quickly mail or send via whatsapp... and today you're taking a lot of photos at an event that you really would need in maximum resolution for editing and printing. You happily take a lot of pictures during the event and later notice that all photos have been taken in low resolution mode. I think it has its place somewhere on the screen.