[wtbob]

> But it does not follow that it's one's responsibility to marry and have kids. There have been plenty of people who contributed a lot to society without ever marrying or raising kids.

One's responsibility is to do the right thing, to do one's duty. For some folks, that duty has not been to form a family, but for the vast majority of folks their duty has been to do exactly that: to repay their ancestors' millions of years of evolutionary investment by investing in their descendants.

There are some folks who have repaid that rather massive debt in other ways, but they are few and far between; far more these days simply renege on it.