^Right. Creatively it's self-evident why the character's focus would be on humans, the species that the entire viewing audience (presumably) belongs to, rather than on imaginary aliens whose creative purpose is to serve as allegories for aspects of humanity.
You'd be hard-pressed to find a science fiction franchise where humans aren't central. In Doctor Who
, humans are the Doctor's favorite species even though he can travel the universe and visit every species that's ever lived. In Babylon 5
, humans are the one species with the religious and cultural diversity that the other Planet-of-Hats aliens lack, the one species that's able to stand up to the Vorlons and Shadows and tell them to mind their own business, and the one species that's able to unify the others into an interstellar alliance. In David Brin's Uplift universe, humans are the newest and least powerful civilization in the galaxy, but are unique in that they evolved intelligence spontaneously rather than having been uplifted by an alien race, and that puts them at the heart of many galactic controversies and power struggles. And there are plenty of SF universes, from Asimov's Empire-Foundation universe to Moore's Galactica-Caprica
universe, where humans are the only intelligent life around.