In the early years of communist rule in China, a sewing machine was one of the so-called big items that indicated a high living standard.
VOA: standard.2009.09.28
Not only is he scrupulously moral and thus vulnerable to all the guilty pangs of wayward husbandhood, but Lin's travails occur in a place--communist China--and during a time--the early 1960s to the early '80s--when literally all occasions conspire against the quest for such a trivial thing as personal happiness.