Revealing mistake: Bo and Luke Duke's car the "general Lee" usually has no glass in the side windows due the doors being welded shut as per NASCAR regulations which is why they climb through the windows to enter and leave the car, but when the general is doing one of its many jumps, in the long shots there is glass in the side windows.
Revealing mistake: In the driver closeup shots, look at the backgrounds. A lot of the time, it shows the vehicle making turns, and the driver doesn't match the motion. Also, there are a lot of closeups where you see blue screen instead of scenery, or they go from city to country in a moment.
Answer: Various reasons, but mainly to drive the Dukes out of Hazzard County because the family have been foiling his schemes since his and Uncle Jesse's bootlegging days.
Captain Defenestrator