Or, the weapon is slaved to the helmet of the pilot.
My handwave is that the weapons can fire themselves, automatically. I mean, why not? The computer tracks the enemy and fires at the most opportune time.
But, human interaction with the weapon brings with it two important variables.
First, manufacturers do not make automatically firing ship board weapons. People don't trust computers to make firing decisions. If they did, their would be a lot of pirates claiming to be civilians with weapons that automatically fired, when the pirates were caught. Plus, there'd be some un-wanted accidents when the computer fired and should not have at a friendly vessel.
So, a human must be involved in the firing process--a human must press trigger or firing stud (especially when dealing with powerful weapons, like some missiles).
Second, human skill can improve upon the computer's fact-based targeting. Ever had Good maps plot out directions for you? Not always does the computer provide the best route. A driver may know about construction on a street, or something to that effect, and alter the base route provided by the software. The same goes for Traveller computer targeting. A gunner may tweak a firing solution based on his expertise.
What would be interesting is a scenario where the players encounter a ship where the weapons are slaved completely to the ship's computer, and a false target happens....
