This is down to the Day light running lights being so bright that most people don't no they don't have the lights on as they can see and be seen from the front so the assume that lights are on.

I have a Range Rover Sport and the rears come on at the same time during the day but it's not a issue for me as the lights are left on auto so at the times when light fades the main lights come on.

DRL's should be set up with auto lights as so many cars drive with no rear lights lite.