As of now, if you would like to do all of the sex things with someone of the opposite gender without yielding a squalling newborn, you basically have two non-permanent options: you can use condoms, or the woman can take care of it (via birth control pills, an IUD, a diaphragm, etc.). As a woman who uses contraception, you're responsible for obtaining it, making sure it ends up inside of you, not losing it, not forgetting about it, and so on — meanwhile, the men with whom you fornicate get to sit on the couch eating Fritos without a care in the world. Very unfair.
Preventing unwanted and unplanned pregnancies is hugely important for both men and women — so why do we think that it should be women's sole responsibility to take care of any non-condom business? At the present moment, research for male birth control is 50 years behind research on female contraception. 50 years! That's two Rihanna-lifes of time. According to the National Institutes of Health, that difference isn't the result of the complexity of suppressing male fertility — it's due "to social and economic/commercial constraints." We tend to not think developing reliable male birth control is important, and birth control research isn't as well-funded as other types of clinical trials.