On the old Dick Van Dyke show from the early 1960s, network censors were careful not to have Mary Tyler Moore's skirts "cup" too much -- which is when the back of the skirt wraps too far under the curves of the rear end.Let us never--and I mean never--forget William Ware Theiss and his Theory of Titilation: if you show a part of a woman's body we are not used to seeing or give the empty promise that we can see more if, I dunno, the dress were to say slip off or we were to turn our heads a certain way, we get more of an erotic charge. He was right about that.
Of course she could wear capri pants that showed far more of the shape of the ass, but there is something more "erotic" (and hence a no-no in 1962) about a "cupping" skirt.