Think it through. The auto companies didn't need any true downtown offices. Detroit didn't have a stock exchange or a commodities exchange. Detroit banks were not large regional banks with the need for huge headquarters buildings and they did very little "investment banking" business. Even in its heyday, Detroit just didn't require so much office space downtown.

The buildings downtown had some suites of larger firms, but most of them were divided up into little offices for individual doctors, dentists, lawyers, and bookkeepers.