For a man, a woman is a companion, not a total mental/emotional/social circuit.
WBUR 90.9 has produced a discussion on social isolation, marriage, and love. It seems that the xenophobic and isolationist tendencies of Americans during the 20th century and especially since the 1970's and spiking in the 1980's have produced a far closer reliance on the marriage/sexual relationship. For some it may be asked to fulfill the role previously supplied or enjoyed through friendships and other relationships.
Automobile, internet, television, cynicism, money.
We've seen a dramatic reversal of the xenophobic element, to the point of [periodically] pouring the heart out to total strangers and psychologists. There is no more town square, and it has been replaced by the chatroom and the marriage.
This can be compared to the Rubens tube and a wave measuring distance/density. The stranger, being very distant socially, has become upswung, the normal close relationships have been downswung, and the very close relationships have been far upswung. This is in response to an intensification of social Hz.