Why Waiting in Line Is Torture:

Fairness also dictates that the length of a line should be commensurate with the value of the product or service for which we’re waiting. The more valuable it is, the longer one is willing to wait for it. Hence the supermarket express line, a rare, socially sanctioned violation of first come first served, based on the assumption that no reasonable person thinks a child buying a candy bar should wait behind an old man stocking up on provisions for the Mayan apocalypse.