Question

Why did the tribes not attempt to produce surplus?

Answer 1

because they believe that what God gave them was enough for them.

Answer 2

They did not require it. To produce surplus, they had to exploit Mother Earth in some way or the other. They are very peaceful and do not usually have trade relations with outsiders. They are self-contained and do not know what will they do of the surplus or of the money they will get from surplus.