At least San Jose is in a pretty nice area, with a good climate, and access to some nice places (beaches to the SE, San Francisco an hour north, hills to the west and east). That's got to count for something.
Bingo. There are people that would happily move to SJ for all those things but don't because it's expensive. If tech died and that part of SJ/SV's economy dried up, plenty of people would move in with other things.
Detroit is surrounded by some pretty nice places as well. Ann Arbor is a great town. And Lakes Michigan, Huron and Superior are really pretty in the summer. I guess what I'm trying to say is that we're not talking about some landlocked post-apocalyptic industrial wasteland.
Having grown up in Michigan and since moved to Silicon Valley, I can say that Detroit and San Jose are not really comparable. The weather in San Jose is much, much nicer. It's sunny and warm most of the year. The four-month winters in Detroit, with their freezing cold and grey skies, are never going to have the same kind of draw.
Ann Arbor is indeed a nice town, and is a reason that people might want to live in Ann Arbor. Living in Detroit so that one might occasionally visit Ann Arbor an hour away makes no sense.
It's true, we're not talking about a landlocked post-apocalyptic industrial wasteland. But it pretty much is an industrial wasteland. An apocalyptic de-industrializing wasteland, if the ever-ongoing decline of the Big Three auto companies can be regarded as a sort of creeping apocalypse.
