Why is coasting down hill bad?

Answer 1

Coasting requires you to put the gear into neutral and let the car freewheel down the hill. If you came to a bend on the hill and someone was speeding up the hill, you may not have enough time to react and slam on the brakes, or slow down. When you aren't in gear, you have less control of your car, as opposed to if you was in gear. E.g. If you were in gear and slammed on the brakes, your car would stall, jerk you forward and stop, however because you aren't in gear, your car won't stop rolling.

(It's why you can push your car when it's out of gear, but you can't push it when it's in gear).