I'm fine encouraging things in the fluff - obviously humans are the dominant species of the Empire and the most populous species in the Star Wars galaxy. There are significant benefits to being human aside from their chargen mechanics. Those mechanics are just the icing on a very nice cake.
Humans being the most significant in movies is kind of a no-brainer: they're the most-relatable by the audience (for obvious reasons) and also the least budget-heavy (not requiring as elaborate of costumes). Humans aren't inherently "better" or "more heroic" than any alien though.
Edited by Kshatriya