The problem with origin stories is if you tell every tiny detail about every secondary and tertiary character and how they got where they are, you have not only a very long movie but a very boring one.
Another thing: can you imagine the outcry if JJ didn't
include McCoy and Uhura and Chekov in this movie? How many millions of people would be saying "Dr. Boyce? Where's McCoy?" "Who the hell is Piper?"
You can't have everything in two hours. Hell, you can't have everything period
. You don't think you'll like it? Don't go. Leave the rest of us who want to see it alone.