That's when they fight. And are they technicians because they're lesser caste or by training? Even Mechwarriors get mech repair training. I suppose it's one of those hypocritical and contradictory clan things. Give a rifle to a tech and get reaved. Give control of a warships weapons to a tech get a medal.
The crew actually are Technician caste, with appropriate Laborer caste for the non-technical jobs, presumably cargo handlers, cooks, etc. Command staff on a combat vessel will be Warriors, with Merchants running non-combat ones, although even they can end up with a Warrior captain.
The Clans probably justify it on the basis that even for weapons under local control, the gunner is still more of a systems manager, with computers doing the actual aiming and firing at the designated target, all under the supervision of the Warrior or Warriors in command. For more centralized fire control, such as Alan Grant posted about the Noruff, they're there mostly for backup in the result of system failure or damage, and making sure that the weapons are actually functioning, with the commanding Warriors even more directly in control.
ASFs will encounter the same range issues in space, so Aerospace Pilots are also unable to see the target and instead rely upon computer systems to do the aiming and shooting. So, it's the command and control by a Warrior that's viewed as what's important.
Just to come back to the aiming and shooting part: as Jellico points out, in space you don't even see the enemy, instead they're just pixels on your sensor display. Given the ranges and speeds involved, just as it's not possibly for gunners and pilots to see the enemy, it's not going to be possible for them to pull the trigger in that split second when the guns line up. Instead, once the command is given to fire, the system will trigger the weapons once it detects that they're lined up, with either micro-adjustments of the course or some degree of flexible mounting being used to bring the armament to bear on target.
Of course, in an atmosphere, it can be very different, with actual visual sighting being possible, but those same systems are already in place. All that happens there, is that there's possibly an extra target cueing option related to visual tracking, plus less of a delay between the fire command being given and the actual shot being taken. Even more primitive direct aiming and firing may be available for the gunner in an atmosphere, giving a last resort backup in case of damage or system failure, but I doubt even the Clans are going to cry blasphemy over that given the likely dire straits involved.