Then why are you saying there needs to be a reason for it or it's diversity for the sake of diversity?
Because it is. Anything not adding to the story itself is extra.
If you want planet Earth represented accurately by racial demographics over half the cast would have to be Asian. If there were 10 main characters, 6 would be Asian, 2 whites and 2 blacks. You have to enlarge the crew if you wanted "other". And because it's Star Trek, someone's gonna get shorted because you have to have an alien as well. That would be your perfectly diverse crew. Which, if the stories were good, shouldn't matter, but then it starts getting obvious what they are doing and it distracts. Even action movies can have to many explosions.
Jesus Christ I'm not arguing against diversity. sheesh.