Suppose that the mad scientists working in their labs one day stumble across the elixer of eternal life. Its easy to mass produce, and drinking it will make you BIOLOGICALLY immortal. This means you won't age or die from disease, but if you get cleaved in the head with an axe, you're pretty much gone. Think elf immortality.
There's a problem however. If everyone is immortal, and having kids who are also immortal, who will also have kids that are immortal, we're gonna run out of room pretty damn fast. So, the catch is that you have to get a vasectomy if you're a man or your tubes tied if you're a woman and be completely unable to have children for the rest of your ungodly lifespan.
Would you take the offer? Would you take it if it instead came not just at the cost of being able to have children, but at the cost of never having sex again?