One sort of addressed in Disney Phineas & Ferb: Star Wars, which is inexplicably and inexcusably NOT canon, somehow. Yes, I grant that there are broad comic elements that might be difficult to reconcile with the more epic tone aimed for in the Star Wars universe. Counterpoint: midichlorians, the inability of stormtroopers to shoot, the unlikely career arc of Jar-Jar Binks, and goram death sticks and robot waitresses. So, sure, let’s keep all of that in the official universe, but God forbid that there’d be room for a Dark Side-infused sub sandwich…
…But I digress.
Tarkin was trying to turn it in to the command center for the imperial military. Think the Pentagon, but it is a giant airship that can shoot nukes. If nothing else, it is a military base. There were supposedly 2 million imperial personnel on board (or some such). Frankly, it feels much smaller. Like the only places that are actually in use are a couple acres of surface right around where the Falcon got pulled in, an elevator to the power station at the center, and the guys who inexplicably stand next to the giant laser of doom.
Command and control, and large logistics transportation. It can make the jump the light speed, after all, to travel between star systems. But primary role wasn’t to be used but to threatened to be used. The fear of it would keep local systems in line without the bureaucracy of the Senate.
Further commentary starts to wander into the Topics Not Discussed Here, so I will it at that