Well the sperm is in the male.. DUH!! And the egg is in the female. When both the female and male have sex the sperm goes into the vagina and finds an egg to make a baby. Sorry if that didn't quite...
Why are there so many acorns on an Oak tree? Same reason, to improve the odds that at least one manages to make the trip and carry on the species. Nature uses overkill on a lot of things.