Why did Arthur Miller chose the occupation of a salesman as the central character of this play?

There is a cruel irony in Willy's chosen role has he does not really have the capacity to sell a dream or even be part of it. Salesmen at the time the play is set needed to be future -thinking cut and thrust characters with youth, wit charm and determination on their side. Willy is in his sixties, overweight, mentally exhausted and unpopular. He is unable to see how selling is no longer about loyalty and contacts. His position represents the superficiality and cruelty of consumerism.