It would be interesting to document what everybody takes for granted, as you imply.
A few points, however: the number of elderly is growing relative to the rest of the population, while the number of young is going to shrink; the proportion of 'older-older' is growing as well; medical and housing for the elderly are much more expensive (and growing faster) than comparables for kids. Medical costs for those in the final years of life are out of sight now for the vast majority of households. Parents would use housing even if they didn't have kids, and not necessarily much less. Grandparents get unpaid for services too if they are not institutionalized.
The biggest point, however, is that the elderly are served largely by the Federal budget, and it is Federal fiscal policy which is politically crippled by popular delusions fed by the right and center, at the very least, about public debt.
mbs