Blaming it on the depression is like blaming it on oxygen. There were others that survived, so that's circumstantial, not certain death. I just see a pattern, that they might not have known what they were doing that well, or were bleeders, as they seemed to attract failure which sometimes means, it's causative. Romney made some of his money like that, take over, pocket the cash, and sell it off for debt. I'm sure my contact over at the Stude museum would refute me, but having spent more than three decades in business, you see and smell things... So what brought down Packard, might be a wider question than self infliction - a little help from my friends...
I agree with Fred, ECAnthony, et al, the more prestigeous and desirable the car, the more the dealer becomes a destination, people with means want the car regardless, and the convenience factor diminishes. Koenigsegg has, what, maybe 16 dealers ...worldwide!!?, yet has increasingly prospered and lived on their lust factor for almost 30 years now.
imho the depression and lack of market is what killed P-A and Duesenberg, not the dealership location/convenience.