What we need is more children. But the US has aborted most of the people who would have been supporting these grandparents, and those who weren’t aborted were simply never born because of the anti-child mentality that took over the US in the 1960s.
However, even if the elderly aren’t producers, they are markets for various services, and this is something that younger people have to bear in mind before they exterminate anybody over the age of 30 or whatever is the current top cut-off point for full humanity.
Some young people will just say "Kill them and take their stuff".