Just think about it: who bears most of the risk in case of pregnancy? Women.
That's the commonly held belief. However, in modern society, men are held accountable for their actions, and many women are perfectly willing to do nefarious things to keep a man around. Read: missing pills, poking holes in condoms, fishing used condoms out of trash, etc. Also, be aware that female birth control pills fail for the entire month if the woman takes any kind of antibiotic that month.
FEMALE BIRTH CONTROL PILLS FAIL FOR THE ENTIRE MONTH IF THE WOMAN TAKES ANY KIND OF ANTIBIOTIC THAT MONTH.
Repeated for emphasis. I can't count on two hands the amount of friends of mine that have accidentally impregnated a woman who took an antibiotic and didn't know about this side effect. And when accidental pregnancies occur, the man must defer to the woman's beliefs on whether abortion is wrong.
It might be unjust, but in most societies, men can walk away and abandon women they've gotten pregnant easily without serious social stigma or financial repercussions.
This is a modern society of hair-trigger lawsuits. Most women won't put up with that. Also, most men actually have at least minimal moral standards for themselves and won't abandon their child and its mother to fend for themselves.
We need more male contraceptive methods. Hell, we need as many contraceptive methods as we can get. If it were up to me, everyone would be required to use at least three methods before having sex. Unintended pregnancies destroy lives, so let's be smart about this.