Why have the Americans developed space shuttle according to the passage?

Ever since the Apollo moon landings, the idea of human expeditions to the Mars has come up repeatedly as the kind of grand adventures that would give focus, purpose, and inspirational lift to the space program. But confronted with the cost — estimated at $ 150 billion last week — presidents starting with Richard Nixon and others have flinched and resorted to halfway measures like the shuttle.

Sweden’s rejection of the European Union’s common currency was a coldly rational statement of mistrust in the euro. It distanced itself from the stagnant economic performance of the euro zone, and flatly refused to place its monetary future under the sway of big countries like France and Germany, who have bent the euro’s rules to suit themselves.