Why attach a propeller to a perfectly normal car? Because you can! Because you can rid the car of transmission, clutch and brakes. Because you can utilize air power and powerful aircraft engines, gain lots of traction and never have to worry about wheelspins or getting stuck in snow or mud.
Some of these cars are even today seen running at the shows. Most models feature sluggish low-speed acceleration, great maximum speed, bad fuel economy and a ridiculous noise from propellers. All this does not take away from awesomeness of owing one.