Did TOS set the precedent for the medical doctor to play such a big role?
I can imagine a show without a doctor. But in all the shows the doctor plays a big role.
I'm trying to think this back and McKoy was such a brilliant character I can see that starting the entire trend. I'm unsure if there was a trend in TV before that for a medical doctor. Anyone know?
If your premise has characters facing danger somewhat frequently, it makes sense to have someone who can heal around.
Also, with so many unknown space-originating ailments, it's creepy to hear a doctor of high rank say "I don't know what this is or how to fix it." It adds to the stakes of the show.
Stories often have an author-as-character, where the writer(s) use a certain wise character to voice their own opinions.
Adaptations of Sherlock Holmes? Doc Watson is the narrator of their stories and sometimes (not very often though) shows his medical knowledge as an ex military surgeon.