Not General Motors, or IBM, or Kodak. And for most small businesses there are few costs that are controllable, but there is one occupancy. Barring massive public subsidies, you cannot build new and rent cheap. Older and historic buildings often provide the affordable rent that allows small businesses to get started. That's Smart Growth.
Business districts are sustainably successful where there is a diversity of businesses.
And that diverse business mix requires a diverse range of rental rates. Only in downtowns and older commercial neighborhoods is there such diversity. Try finding any rental rate diversity in the regional shopping center or the so called office park. There ain't none. Older business districts with their diverse rents are Smart Growth.