That was likely added to quell reactions to a woman as a first officer. But the Network had notes even so on how negatively test audiences reacted to Majel Barrett’s Number One.
Roddenberry tried another tack with blonde, beehived, Whitney in a miniskirt as Yeoman Janice Rand. She was supposed to be a woman main character but even that was too much for the executives and she was written out by the end of the first season.