"Why don't they make a birth control pill for men?"
There are important considerations from medical ethics that might explain why a birth control pill for men has not happened yet.
You'd think that there would be an ethical impetus for the development of a birth control pill for men, given that men (or at least, their sperm) are a necessary component of human reproduction and that men have an interest in controlling their fertility, too. Men might view such a pill as a useful option. The question is whether that benefit outweighs the potential risks.
The Belmont Report (which lays out the U.S. government's guidelines for the protection of human research subjects) notes that ethical treatment of humans requires beneficence, which includes maximizing the possible benefits and minimizing the possible harms of a particular intervention. In biomedical research, these risks and benefits are usually understood in biomedical terms -- what will happen to your health with the intervention or without it. If an intervention introduces too much risk of harm, or too little chance of benefit given the potential harm, it crosses an ethical line.
For the female partner in human reproduction, this means tallying the possible health consequences of taking the pill against the possible health consequences of pregnancy. From this point of view, even if oral contraceptives increase your chance of weight gain, blood clots, and stroke, the potential harms of the pill are less than the potential harms of pregnancy itself (which include high blood pressure, gestational diabetes, and death, not to mention weight gain).
For the male partner in the equation, the consideration of risks and benefits is complicated by the fact that men don't get pregnant. As such, any potential harms that come from a male contraceptive would count against the ethical use of that contraceptive, since there is no impact on a man's health (at least from a straightforward physiological perspective) from impregnating someone. This is part of the reason it's possible for men to be fathers without knowing that they are fathers. The analogous situation hardly ever happens with mothers.
In short, unless the male contraceptive provides some clear health benefit to the male taking it, researchers will judge that the possible harms outweigh the possible benefits.
Indeed, this kind of assessment may explain why the human papillomavirus (HPV) vaccine was initially tested for use just on girls, even though males get HPV, spread it to their sexual partners, and can get warts or even penile cancer from it. While bothersome, genital warts are less harmful than cervical cancer, the most serious female consequence of HPV, and penile cancer is much rarer than cervical cancer. But researchers are now testing HPV vaccines on males in the hopes that the potential harms will be even lower than the (comparatively) low potential harms of HPV.
It looks like an attempt to avoid putting an undue burden on men (by offering them a pill with more direct health risks than health benefits) ends up saddling women with an undue burden as far as the responsibility for avoiding pregnancy. Maybe this means that our evaluation of risks and benefits needs to take more account of social factors -- including the real (if not physiological) benefit a man could get from knowing he will not unintentionally impregnate his partner.