This viewpoint is often a result of Most Writers Are Male, and/or a (possibly unconscious) assumption that the audience is mostly or exclusively male, but is sometimes enforced by the money people to appeal to potential consumers, even in works by women or intended for a female audience. One of the reasons for this is that advertisers prefer shows targeted to young men, because young men are more easily swayed by advertising.
Common symptoms of Male Gaze include assuming that the audience will identify or empathize primarily with male characters, and will have typically male experiences, preferences and expectations. (The former is actually enforced in Young Adult publishing, as it is an accepted fact that boys dislike reading books about girls and thus general-audience YA novels must have male leads.)
This is by no means a new phenomenon - see this picture (NSFW) of Mary Magdalene, done in the 1500s. The story runs that towards the end of her life, she became a hermit, and grew her hair so long she didn't need clothes. Nevertheless, the painter has decided to paint her without the hair covering everything that it otherwise might, and not as a particularly old woman.