Not THE inspiration, but AN inspiration. Siegel and Shuster made several versions of Superman until they got it right.
This is Kal-L, also known as the Golden Age Superman. He didn't fly. He ran everywhere and jumped 1/8 of a mile. Through the power of inflation, he would eventually become the most powerful hero on Earth.
Governments are fearful, pathetic things, mostly composed of individuals seeking to retain access to whatever powers their roles in office afford them. Imagine, for a moment, if a being such as Superman were to exist on our Earth.
Short Answer: Because it took too long to cross town in 700 foot leaps.
You don't tug on Superman's Cape. You just don't do it. Few superheroes in the DC Universe would even consider entering the ring with Big Blue.
No powers, no cape, no money, no problem Superman isn't completely super. Almost Superman doesn't have the same ring, though. If you have been reading the Man of Steel recently, you may have discovered he doesn't have his full range of abilities any longer. Hence the motorcycle, biker shirt, jeans, boots and military style crew cut.
