Visible crew/equipment: When Ethel's on the stoop in front of the building waiting for Lucy and Ricky, right before Ethel asks Ricky about Lucy's driving lesson, just as Ricky drives up we can see cables moving in front of the new Pontiac pulling the car. Then, when Ethel crashes the new Pontiac into the old car, the jiggling cables are again in front of the new car. Lastly, when Lucy finally starts the old car's engine, now there's a moving cable in front of the old car as well. (00:09:50)
Revealing mistake: Look closely at the Ricardos' new Pontiac convertible. There is no glass within the windshield frame.
Visible crew/equipment: When Lucy's sitting on the piano looking out the window at their new car, just as Ricky walks into the living room we can see the shadow of the mic equipment moving overhead, likely adjusting to the actor's position. (00:07:10)
Answer: There is no reason. It's a just a silly plot device, typical of the era. Women characters were often portrayed as making uninformed assumptions or decisions.
raywest ★