GM does not "own" the GM dealerships any more than a shopping mall. GM dealerships are independently owned and operated.
Nor are dealerships always located in convenient areas for charging. For example dealerships are often not located near shopping or restaurant locations.
Frankly... The whole point for eh Volt is that I don't have to stop anywhere but my own garage to charge. I simply don't need fast charging capability because the Volt has a range extender for the rare occurrences I need more range.