Why does the cell divide twice in the process of meiosis?

Because the chromosomes are still duplicated after the first division. The second division cause the new cells to end up with half of the number of chromosomes of the parents cell.

Meiosis is a reduction division meaning it needs to reduce the number of chromosomes to half. The first division (MEIOSIS I) only includes the separation of homologous chromosomes or tetrads, the second division (MEIOSIS II) is the same as mitosis, meaning it separates sister chromatids from each other, resulting to half the number of chromosomes from the parent