Personal theory: since humanity (i.e., regular humans) will continue to exist, less the resurrected and transformed Christians, all those planets and solar systems exist to house the ever-growing population of people. The saints will supervise angels in terra-forming those planets to make them fit for human existence, and so humanity will spread (light speed no longer being a limit) throughout the universes infinitely.
I think that is an equally valid theory. The brain spins when one thinks about all the stuff NOT mentioned regarding eternity and the universe, and just unbelievably huge and incomprehensibly infinite it is. It’s hard to imagine that it is all there (including the part we can’t see) just to give us twinkly stars.