It's called "drama" and only so much time to tell a story. I tell people I do work for that you can't run off into tangents too far when telling a story. Archetypes are necessary if it means you can do less explaining to the audience and spend more time on the story. It's a show about space adventures, not showing how…

It means they lost a 6th of the Star Trek audience and had to rely on several retoolings just to keep that.