Why is the arrangement of the chromosomes at the end of metaphase important?

In metaphase, chromosomes line up in the middle.
This is important because if the chromosomes did not line up in the middle of the cell, then when it divides, the two resulting (divided) cells would not have equal numbers of chromatids (like half of a chromosomes).

*Unequal number of chromatids in the divided resulting cells would undoubtedly cause problems!!!