Why millions of sperms produced in male even though one sperm is enough to fertilize an egg?

Large number of sperms have to travel a long distance from the region of cervix to oviduct or fallopian tube before they meet the egg in the female genital tract. The life span of a sperm is about 24-48 hours after their deposition at cervix in the vaginal canal. During the course of their travel to reach the egg in oviduct many of the sperms die on their way.  During their travel they have to over come the acidic conditions of female genital tract to reach and surround the egg. So, a few of the sperms only successfully reach the egg and out of which one of the active sperm  only fertilize the egg.