Even after learning the approximate location of the other two villages, Rein did not immediately attack them. He was planning to search the whole floor thoroughly, so no matter what, he was definitely going to come across the remaining two villages. So instead of attacking the village he decided to continue doing their investigation of the floor just like before.
Outside the village, Rein's group were unable to find any other treasures at all even after searching the majority of this floor. From this it was evident that the main challenge of this floor was actually the villages and everything else was just there to act as minor inconveniences.
But still Rein was not hundred percent sure that the desert area did not have any treasure. There was a slight chance that this endless desert was hiding a very rare and well hidden treasure. So even if it was wasteful, he was still going to search every nook and cranny of this floor.
