Revealing mistake: At the Brown Derby, when Lucy bumps into the waiter causing him to trip and spill the tray all over William Holden, we can see that the waiter's hand is taped to the bottom of the tray for the stunt to be done efficiently. (00:15:15)
Continuity mistake: At the start, when the Pontiac convertible turns into the driveway of what should be the Beverly Palms Hotel, the sign with the real name of the hotel can be seen, which reads Beverly Carlton Hotel.
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 ★