Der Spiegel has the story:
During his trip to Germany on Wednesday, the main highlight of George W. Bush's trip was meant to be a "town hall"-style meeting with average Germans. But with the German government unwilling to permit a scripted event with questions approved in advance, the White House has quietly put the event on ice. Was Bush afraid the event might focus on prickly questions about Iraq and Iran rather than the rosy future he's been touting in Europe this week?
It's probably mostly because he's an idiot and can't answer questions unless someone gives him the answers in advance. He could have worn that device used during the debates with Kerry, I suppose, but the Germans might not have allowed that either. Apparently they are less sheep-like than Americans - or maybe they still operate under a democracy with a free press. Makes me yearn for the good old days.