Here's why:

* Diploid cells have two sets of chromosomes (one set from each parent). This is the typical state of most body cells, also known as somatic cells. They are responsible for building and maintaining the body.

* Haploid cells have only one set of chromosomes. These are the sex cells (sperm and egg), also known as gametes. They are involved in reproduction and are responsible for carrying genetic information from the parents to the offspring.

In summary:

* Somatic cells (most cells in the body): Diploid

* Gametes (sex cells): Haploid