Helicopters do not have a lot going for them. They are expensive to buy as well as operate, somewhat odd-looking, and, if movies like Die Hard 3 and Cliffhanger are reliable sources of information, they can be brought down with a hand gun or a rock or some rope... pretty much anything nearby.
Helicopters are fairly vulnerable pieces of hardware, but it takes more than a knock in the rotor to drop them out of the sky.
I have traveled by planes, trains and automobiles, but never by helicopter. From an engineering standpoint, they scare me. Where possible, it is good to avoid single-point-failure scenarios. If one airplane engine were to fail, most airplanes can still be flown with the remaining engines. If the main rotor blade of a helicopter were to fail mid-flight, down it goes. The main rotor is responsible for the lift force, and without it, it is time to look for a good parachute (and then a good lawyer).
How does a helicopter navigate around? The principal force is generated by the main rotor, which spins very quickly, displacing vast amounts of air in exchange for lift upwards. If it wants to maintain altitude, the lift force upwards must be equal to the weight downwards.
