Question

Geographers divide the world into different regions:

because it is required by national geography standards
to compare different places
to slow down worldwide trade
because regions are clearly defined

Answer 1

The planet is a big big place. It much easier to study and understand it if it is broken down into more manageable bits. Its much easier to deal with just tropical regions or arctic regions alone that the whole planet at one time. And it helps to have geographers that specialize in different regions so that we all can have a better understanding of each one.

Of course cultural geographers have even more regions to deal with.