The Star Wars galaxy is incredibly vast, but the franchise's video games rarely use a main character that's not human. As a whole, Star Wars tends to focus on humans likely because they are more relatable for the audience. As a medium, video games have the benefit of interactivity to bolster player sympathies toward a protagonist, and the under-utilized aliens of Star Wars offer unexplored perspectives.
Giving the player control of a human Star Wars character has a broad appeal, not just because it's a convenient self-insert for the player, but also because humans in the fictional galaxy are numerous and fill nearly every conceivable niche. Humans are by far the most common and widespread species to appear throughout the franchise, and are so varied that their home world isn't even known for certain (it's presumed to be Coruscant). This makes it easier to create a protagonist like Star Wars Jedi: Fallen Order's Cal Kestis or Battlefront II's Iden Versio, where there are no alien cultural influences to structure the narrative around.
Both of those games' plots heavily involve the Galactic Empire, a primarily human power structure, but the focus on humans continues to push the stories of Star Wars' aliens to the periphery. Fallen Order, for example, features Greez Dritus, pilot of the Stinger Mantis. His gambling debt to the Haxion Brood crime syndicate is only explored when it affects Cal directly. Merrin, a Nightsister from Dathomir, similarly has a compelling perspective on the galaxy, but ends up feeling like a token alien character. Being able to use Merrin's Nightsister magick from Fallen Order would alone be a compelling reason to maker her or another Nightsister a protagonist.
Alien Protagonists Broaden The Possibilities Of Star Wars Games
Exclusively focusing on human main characters is a disservice to the Star Wars universe. The live-action series are finally getting around to featuring an alien protagonist with Ahsoka Tano, a Togruta, but games since the Disney buyout of Lucasfilm in 2012 haven't done much to expand the galaxy's perspective when it comes to leading roles. Even just giving players the option of being an alien would be a nice step. RPGs like The Elder Scrolls prove the player character's species can be a relatively minor detail, more or less only affecting the player's perception of the story.
Star Wars stories tend to be character driven, though, and any sort of diversity would be welcome. The Fallen Order developers pushed for a black lead, and even considered an alien protagonist, according to an interview Fallen Order director Stig Asmussen did with Game Informer, but there was a worry that the latter would "alienate" fans. Asmussen even mentioned that he thinks "it would be really cool to have an alien protagonist," yet the general direction of the franchise continues to highlight almost exclusively human-centric stories. The rationale of aliens not being relatable is rather thin, since there are numerous species in Star Wars that speak Galactic Basic (i.e. English for English-speaking audiences) and are quite humanoid. Recent blockbuster Star Wars games have tended to play it rather safe with human main characters in established time periods and settings, but adopting an alien protagonist could provide any number of unique and interesting perspectives.
Source: Game Informer/YouTube