After asking this question and reading more in the Wookiepedia and thinking about how everything in Star Wars seems to be just so much bigger than life (or most imaginations), I started thinking about the Imperial ships.
I read somewhere that the original Death Star had a crew of over 1.5 million on board. The crew complements for Imperial Star Destroyers and Superstar Destroyers are also quite large, although not as large as the Death Star. Just moving the crew from various planets onto the ship to fully staff it would require an amazing feat of logistics.
Also there's the matter of the amount of material used in such large ships. It would be a significant amount to take out of any one planet, but considering the materials needed, that would involve mining the materials on many planets and transporting such large loads to a construction site. Supposedly the Death Star II was built in only a few years, after the first one was blown up and it was also much larger.
The Death Star II was also fully operational with extremely large sections of it uncompleted or not even started.
All this raises two questions:
1) Are the Imperial ships bigger than they need to be?
2) Is it even possible, considering logistics of construction and staffing, to be able to create such large ships?
I read about the Darksaber, which is essentially a superlaser like the one in the Death Star, but without all the extra mass around it. Since the Death Star is essentially an instrument of destruction, why does it need do do more than support and protect the superlaser? And why do the Star Destroyers need to be so big? While we can say that's for troop transport, considering the size of the destroyer and the amount of troops it could carry, can it move that many troops down to a planet quickly?
In short, are the logistics possible to make ships this large possible and is there really a need for them to be as large as they are?