The rabbinic sages say that the stairway is Sinai. The way to live in both worlds, mundane and spiritual, is to be a Moses-like messenger ascending and descending the mountain, seeking the Divine message and coming back on earth to apply it as a way of life.
Not only does this notion explain the imagery but it answers the question of why the angels in the story olim v’yor’dim bo, “were going up and down”.
If the story had been written from the angels’ point of view, they would have begun by descending from their heavenly habitat, but the story is not for angels but for human beings.
As SM Lehrman, a British rabbi of an earlier generation, used to say, man is both earth-bound and at the same time heaven-bent.