You're right, it's not necessarily true relative to past levels of consumption. But there's a limit to economic growth, and the choice of "paygo" vs "investment

You're right, it's not necessarily true relative to past levels of consumption. But there's a limit to economic growth, and the choice of "paygo" vs "investment" probably only has marginal effects on the rate of economic growth, so the point stands. "Non-producing" people are retirees (as well as children). People who don't produce market goods/services that make up the vast bulk of our material needs.