Advertising lives in the short-form world. Because mass media is so expensive the 30 second commercial is conventional and because there is so much clutter simplified signals are essential to 'cut through'. One form of communication short-hand used as a default is the stereotype -
"A stereotype can be a conventional and oversimplified conception, opinion, or image, based on the assumption that there are attributes that members of the "other group" have in common. Stereotypes are sometimes formed by a previous illusory correlation, a false association between two variables that are loosely correlated if correlated at all. Though generally viewed as negative perceptions, stereotypes may be either positive or negative in tone."
In the 1950's and 60's when men dominated advertising stereotypical impressions of women as inferior or subservient were not only commonplace but usual. It was normal to show women as housekeepers, largely because most were. The contraceptive pill arrived to emancipate women and it was sex that ultimately overcame the inhibitions of gender.
While it is more common for advertising to show men as stupid or infantile now, back then the shoe was on the other foot (which is a curious expression - if you think about it).
Here's a selection of ads that are offensive to our contemporary sensibility but which should give pause for thought about how people are characterised in advertising today. If you scratch the surface you'll see a lot of guilt being applied (still to women) about their role as working mother - much of it condescending. I'll see what I can dredge up to make my point.