From a very early age (and anthropologists might have you believe it's inherent in the gender), women are trained to socialize as a part of being "good," in virtually every culture. Creating a social network helped ancient woman raise children, keep her man, know when the berries on the other side of the ridge were ripe or what made seeds grow faster, and other things that serve the society as a whole. Modern women still network for the same reasons--it does them good in their personal and professional lives, as mothers, employees, daughters, and so on.
So when there is no one to socialize with, women feel the need. They may get a pet for a companion, or join organizations, or gossip with neighbors, or use their offspring as their social contacts.
(Cats are good company because they demand little of humans, equally happy being pampered and ignored.)