Folklore provides a socially sanctioned outlet for the discussion of the forbidden and taboo.
Life, it seems, is nothing if not a series of initiations, transitions, and incorporations.
Polls are frequently taken to try to tease out or determine likely directions and trends, but once taken, they belong to the past, requiring that new polls be taken.
Ancestor worship, or filial piety so characteristic of Asian cultures, for example, does not really resonate with Americans who favor children, not grandparents.
Future orientation is combined with a notion and expectation of progress, and nothing is impossible.
Americans do believe in progress and there is almost certainly a kernel of truth in the joke.