There's a reason for this. OK, so there's a reason. It's the nature of the genetics. It's really not that confusing. I'll keep it simple.
Sex chromosomes define gender.
Each parent contributes one sex chromosome, and these determine the gender of offspring. Females produce only X chromosomes in the form of their egg, but males produce both X and Y chromosomes, propelled in sperm. These eggs and sperm also carry one half of the parent's genetic material, which explains inheritance. Eggs and sperm do not carry the same combination of genes, which explains why all of our offspring don't look identical to one another. When egg and sperm meet, they combine their traits to form a single entity, not unlike pulling two halves of a zipper together.