Our body cells are diploid because they contain the total number of 2n which is the complete number of chromosomes (46)
Which Cells In Your Body Are Diploid?
Body cells are diploid, that is they have "double" the number of chromosomes as your sex cells. Gametes (sex cells) are haploid and contain only half the number of chromosomes as all of your other cells. That's because an egg and a sperm each provide only HALF of the genetic material needed to create an offspring. If they were diploid, the offspring would have way too many chromosomes and never make it past the embryo stage.