It is not a question of whether they do anything important. It is whether they do anything that makes for good gameplay.
IRL, US Navy Navigation Officers are watch standers primarily responsible for ensuring the Quartermasters (what the US Navy calls is navigation enlisted) are keeping track of the ship's location, upcoming hazards, and using secondary methods of reckoning to accuracy check the SatNav. The Quartermasters also maintain all the navigation related gear. In the US Merchant Marine, the navigator is one of the ship's officers (typically the 2nd Mate) and basically does the same thing.
The Helmsman is a completely different job. Master Helmsmen are actually specialists who often have other jobs since helming the ship in normal conditions is not particularly skill intensive. The master helmsman takes over for the rando at the wheel when navigation or the watch officer decides the situation is a high risk situation, such as maneuvering in restricted quarters.
In Traveller terms, a Quartermaster needs Astrogation, Electronics (Sensor Ops), and Mechanics to do their job. A Master Helmsman needs Pilot and whatever their day job is. (One interview I read, the Master Helmsman was a Sonar Tech).
But is that good gameplay to make that distinction? It can be. But it involves giving the Astrogator active, useful tasks that have actual "in adventure" benefits. But if Astrogator is just going to be a help skill for the Pilot and Engineer, it shouldn't be a mandatory ship's role IN THE GAME.
Just like IRL most spies sit at a desk reading stuff. But that isn't what makes for good game play