Why do we have different cultures?

Because of the universal diversity of the globe.

Explanation:

There are different types of people all over the world, and for a long time many of them never met or learned that there were other human beings. All they had was who they knew around them. Therefore traditions formed along with stories and different aspects all depriving from their surroundings and were kept among the coming generations. Creating a ¨culture¨.

Culture is a combination of ideas, that we use to make sense of the world around us, culture is the "whole way of life" of the people living in the culture, and its a struggle between competing ideas - a "whole way of struggle."