MANDOBLE is correct. We lack the reqired features (roads, rivers towns and cities) required to navigate to a target.
AH is a game. Expecting players to be able to do instrument navigation to points they don't have a heading for is unreasonable.
Given the difficulty most players have lining up a bombing run now, requiring instrument navigation to the target (which, unlike fighters, must be precise and you must be level and at an even speed when you get there and have had time to calibrate) would put level bombing beyond the reach of all the the fanatically dedicated.