People get married. They find different jobs and their schedules change. They develop more solitary interests.
An online social life isn’t a social life for me. It’s a social fiction, even though you can have real feelings for the people involved. I would consider a guildmate in an online game a friend in real life, but how many of my guildmates will I ever meet or interact with much in real life? To what extent will I really ever witness what they are like as people out in the world doing their thing? It’s one thing to hear someone say what they do, but it’s another thing to actually be with a person, in person. Physically present.
Some days I have a strong reluctance to come home and sit in front of yet another computer. What was that anime with the ongoing storybook thread about the world where people were all more interested in their machines than in each other? Oh yeah, Chobits. Totally ridiculous anime, but that haunting idea about disconnect from the world, complete world disconnect in fact, stands out as a disturbing image.