It is very simple. It's because guys rule.
You think women's liberation and feminism entitles you to be sexual? Sure! Fine! But you still have to get us and make us the center of your universe. I ask you one question. Which gender do you think invented the thong?
[He admits he's being facetious. Sort of.] But all my analysis tells me men control the terms of the discussion, ... Men control dating arrangements.
I don't think the stakes were so high and I don't think sexuality was so overt.
You need to put this in the context of all the other things we think of as disfiguring that people do because they think they'll be more attractive.
To be grown up is to be settled, comfortable, stable, responsible, and secure. Those are bad conditions for advertising, which depends on our sense of insecurity, anxiety, and incompleteness.