Could it have more to do with near past, namely 1950 nuclear familly ideal? Middle class women were housewifes - which can be very lonely if you don't put effort into keeping relationships. People have to make effort to meet you and if you alienate them, they simply cease to make effort.

Meanwhile men went to work where people have no choice but to communicate with you. You don't have to put effort into relationship, you are guaranteed not to be really lonely. In fact, too much relationship can be detrimental as you all compete for position and salary etc. Being a bit of jerk can pay of and you don't have to care whether people like you - if they don't it is up to them to deal with it. Plus there was influence of past war on expectations on males (be like veterans are).

That leads to two different kind of socializations for boys and girls - where boy socialization leads to loneliness in long term, when you are too old to pick up new habits.