Yeah,,,those indian genuises again. Sitting in the middle of a circle, but never invented the wheel.
Sitting in that circle,,, cant you hear the talk? “dude,,,theres got to be a better way to transport things than dragging it on 2 poles.”
While prairie looks flat, a lot of it is not, and is in fact punctuated by deep draws and badlands terrain. Wheels would not fare as well in such an environment as the travois did, and the travois had the added benefit of utilizing the lodgepoles for the 'house' en route, making something which would have been freight useful as part of the transport device.
YMMV, but crossing the countryside out here with wheels would have been far tougher (wheels need roads).