This trope is the feminine-gender-role version of But Not Too Black. Writers are often hesitant to present a female character with ambition when it comes to a career. In some cultures, women are expected to only have a job until they're married, at which point they'll quit to focus on being a wife and mother, so having a character who dreams of a serious career can suggest that the character lacks femininity and she will be seen as less sympathetic. If the writers want her to be an active, strongly motivated person, but think that people won't relate to an ambitious female, they have a problem on their hands.