Why is it important to adjust the shelves to the correct position before lighting an oven?

It is important to adjust the shelves to the correct position before lighting the oven because it is safer to do so whilst the oven is cold and doing that, you would not put yourself at that much risk of getting burnt as when you are adjusting the shelves whilst the oven is hot. Whether you are doing this whilst the oven is cold or hot, still wear oven gloves!

It really is common sense because if you needed to adjust the shelves but you already turned the oven on and you could feel the heat and knew the oven was really hot, you wouldn't put your hand in there to adjust the shelves anyway.