Why is trade so important for Nomadic and Sedentary tribes?

In ancient times, sedentary tribes only had access to local food and materials. For anything not to be found in their direct living area, they needed the nomadic people who went to other areas and countries. The nomadic tribes on the other hand had to rely on the sedentary tribes for foodstuffs that had to be cultivated.

So trade was important for both parties as they could supply each other with essential means for survival that only the other party could procure.