They're also probably not nearly so automated.
Crew casualities seem to be relatively rare aboard GTVA ships; the only time they're even mentioned is when the GTD Phoenicia takes it on the chin from quad BFReds, which except for ship-guardian ought to blow the Phoenicia away; even then, it's only half or quarter of the crew (I forget which at the moment). That's an impressive achievement.
My guess would be GTVA ships operate on an armored box concept and the majority of the ship we actually see is nothing more than the exterior hull, just like a submarine. It's there for show and extra protection; they probably employ a triple or more hulled design wrapped around a relatively small and heavily armored crew area in the center. There's a lot of space to fill, engineering areas, machining shops; most of these ships probably aren't capable of atmospheric entry and they appear able to conduct operations almost indefinitely, as well as repairing even serious damage in the field. All this is wrapped around the central armored box section as well.
The central armored box houses critical systems such as power, manuvering, and the crew (the last while in combat); crew quarters may be placed outside or inside the box depending on the size of the vessel and other considerations; corvettes I would assume have quarters outside the central box, destroyers inside. In combat, everything outside that armored box is emptied of crew and depressurized. It acts as extra sacrificial armor for the central armored box; if well-compartmented this could actually go long way to explaining the incredible durablity of GTVA craft. Explosions won't transmit through vaccum, so a multiple-hulled design with a lot of sacrificial compartmented space acting as voids could absorb a great deal of raw explosive power, even nuclear and antimatter. A solid-shot armor piercing weapon would be much more effective, but the ability of armor to stop or deflect such a weapon cannot be underestimated. Having once made a study of battleship protective schemes I know just how hard it is to get a round through a well-designed set of defensive armor.
That would also explain the utility of beam cannon; they can't be deflected and a void space won't keep them from transmitting their destructive energy forward to the next bulkhead.
