I'd suspect there's a difference between being able to competently pilot a shuttle and skillfully pilot a giant starship.
USS Excelsior wrote:
It's probably a given that all officers can pilot a shuttle and handle the conn, and when the other Ensigns or Lieutenants are not stationed at the helm of the main bridge then what else are they doing?
The Helm could be a branch of the Engineering department who would have a more intricate understanding of the thrusters and engines they're flying and able to deal with them when they're damaged in a crisis situation, and of course they'd have regular engineering jobs when they don't have shifts at the conn.
And plus why are these Junior officers even in the command division....