Why do gametes contain half the number of chromosomes as body cells?

This is because meoisis division occurs in gamates which are sperm cell and egg cell. And in meoisis division the number of chromosomes for the daughter cells is half the number of chromosomes that the parent cell have. This is because when there is a fussion of male and female sex cells, the zygote which is the daughter cell should have the 46 chromosomes which is the normal chromosomes for humans and when this chromosomes are in pairs then they should be in 23 pairs of chromosomes which are haploid and later be used for another cycle when the person matures and ready to reproduce