I believe it was inspired by the Hyatt Regency ziggurat / atrium / glass elevator deal, which was the height of hotel chic starting circa 1971. The ES paradigm that appeared 10 or 15 years later was a low-rent, easily replicable copy. Hyatts don't have swimming pools right off the center court, though, and I don't think ES designers ever found a way to make their atria stop stinking of chlorine.