Commentary Par XXI 31-33

It is eventually clear (e.g., [Par XXI 64-66]) that all these spirits (compared to all the stars in the nighttime sky), descending, are coming from the Empyrean for the sole purpose of welcoming Dante to his higher degree of contemplative awareness; that they, like all the spirits we see in the heavens, are only temporary visitors to these realms; that all the saved souls and the angels populate the Empyrean (as far as we can tell, they have never manifested themselves to anyone in a lower heaven before Dante's most extraordinary visit to the heavens that concludes his journey through the afterworld).

Jacob saw angels on the ladder in his dream, ascending and descending.  Dante sees the souls of the blessed only descending, at least for now.