Wheeled carts are great, but if you already have a way of solving the problem, why bother?
The wheel itself is not some sudden groundbreaking invention. It's the natural evolution of rolling heavy stone blocks on logs. A roundish log is not hard to make. You get tired of shuttling logs back and forth to move your stone block, so you attach the logs to a frame and put your block on top of that.
Innovation is not a question of are we smart enough to figure it out; it's a question of does this improve things over how we currently do it, i.e., why bother? If you have canals, steep rocky terrain, or thick jungle and you also have lots of slaves, the wheeled cart becomes a "why bother" solution.