Presumably, because their connections are in the Valley and all of the employees/founders would prefer not to move that far.

Given that a key objective was to be closer to their contacts, Detroit would make little sense.

Detroit has terrible weather and worse infrastructure. I grew up there and going back for even a few days is incredibly annoying compared to even a tier-two city like LV or Philadelphia, which at least have things going for them.

Detroit only makes sense if you like drinking or sports; there is nothing else to do there.

Do you want to live in Detroit? Moving to Stockton would be a more inspired choice. Close enough to the valley for the money folks, but generating some positive economic activity in a community that could benefit. Also substantial lower costs which benefits founders.

You first.