Why are many sperm ejected into the woman's body?

Answer 1

Males of every species have an ingrained need to keep their genes alive. The more sperm a male produces and the more eggs a female produces greatly increases the odds that a pregnancy will happen.

Answer 2

Many sperm are ejaculated into the woman's body to increase the chances of fertilization. Sperm need to navigate through the female reproductive tract to reach the egg, and only one sperm cell will successfully fertilize the egg. By releasing many sperm, there is a greater likelihood that one will successfully fertilize the egg.