Because it won't take until 2200 for us to feel the very real effects of an aging population. An aging population means many more people past retirement age, no longer economically productive, and requiring more medical care, skilled nursing, pension or social security income, etc.

It means fewer young workers entering the workforce at the same time, and therefore reduced tax revenue, fewer people paying into insurance plans, fewer people donating to charities, etc.

So there's this distinct one-two punch of having more folks to support, and fewer who are able to support them, regardless of any family structure; this will be a global problem.