You should really read the article but... tl;dr It was 20% cheaper to just have a camel, than to also attach a wheeled cart to it, due to the absence of trees.

You should really read the article but... tl;dr It was 20% cheaper to just have a camel, than to also attach a wheeled cart to it, due to the absence of trees. So the camel beat the wheel for economic reasons alone.