It´s because People aren´t kicked and so People are afraid to log out and keep their game running and stay logged in. So when they come home they can continue playing.
When enough People do this.... well you get the Picture. It´s a disgusting practice, as they prevent other People from playing while they aren´t even remotely near to their computer.

But as long as SE isn´t auto kicking People of the server when they have been AFK for sertain amount of time, be prepared to never able to login for days to come. /facepalm