If you are on a hill such as a driveway and you turn your car on to accessory mode and then forget your car is not turned on you can put your car into gear. if you put your car into reverse and the car starts rolling it is difficult to stop it because you have no power on the brakes and cannot turn the steering wheel because it is locked. this is very dangerous. there may be a child behind a car and it will roll back until you can get it turned off. i don't think you should be able to put the car in drive or reverse when the car is not turned on and your foot is on the break.