I think the acceptance of mathematical expectation of utility or its arithmetic mean was an unthinking carryover from the mathematical theory of the law of large numbers as applied to asymptotic processes.
About This Quote
About Paul Samuelson
Paul Samuelson was a 20th-century American economist and nobel laureate. Paul Anthony Samuelson was an American economist who was the first American to win the Nobel Memorial Prize in Economic Sciences. When awarding the prize in 1970, the Swedish Royal Academies stated that he "has done more than any other contemporary economist to raise the level of scientific analysis in economic theory". Read more on Wikipedia →