How is it that Americans and the world have accepted the US governments account of what happened in 9/11?

Why hasn't there been proper and thorough investigations as to why there are certain inconsistencies about the US government's account of what happened in 9/11. Shouldn't the US government have come out and addressed the public properly as to why they couldn't and weren't possibly involved in the attacks if they truly weren't? Why is it that most of America and the world so freely accept the US government's account of what happened so freely when there are so many inconsistencies in their explanation?