Except Shatner was the star and the focus. When it comes down to it, are you giving more time to the helmsman so he can plot in a new course, or are you giving the lead actor, the one drawing in the viewers, a little more time for an extra line? It's not that difficult a decision to make.
There's no denying Shatner was the star and focus--that is a fact not only from the producers' intent, but a basic observation, just as its a fact the "add on" actors were not intended to be more than positions more tied to a function than being on track for great character growth.
Star Trek's success or audience appeal was not resting on the shoulders of Takei, Nicholls, Doohan, et al.
^^^
This. And if someone wants an example, take TOS'
"The Doomsday Machine". The Communications officer for that ENTIRE episode is a character named
Lt. Palmer played by actress Elizabeth Rogers. Nichelle Nichols (as Uhura) is never once seen or mentioned. Are STS fans outraged by this, and as a result does the episode languish as 'one of the worst' (like say
"And the Children Shall Lead")? Nope. It's consistently rated as one of the better TOS episodes (in many fan's 'Top Ten' lists - including mine.
If that isn't a prime example of how much Nichelle Nichols (and Uhura) actually meant to a person's enjoyment of a given Star trek episode, or the series in general, I don't know what is.