Remember that the Kitty Hawk flights were done "secretly" with the hired photographer and some locals being the only 3rd parties present. The Wright brothers were back in Ohio flying advanced versions of their plane over farm fields before much publicity came of it, and even then almost nobody believed it. It was only when they took a plane to France and flew it around Le Mans that people truly believed.
EDIT - it was Le Mans, not Paris :)
EDIT - it should probably be pointed out that the Wright brothers didn't think that powered flight, in and of itself, was all the useful without a method to control the aircraft. That's what they really worked on and really their most important contribution. There were a lot of people working on flying machines all over the world, but the Wright brothers had radically different ideas on how to control the aircraft (and ultimately they were correct). So there was a lot of incentive for others in the flying community to discount their success until it was too late to deny it.