Yep. People that don't want to or can't commit as much time or as regularly often choose to play NPCs. There's a DM or a DM committee on site that observes the game directly or through their NPCs and uses the NPCs to steer the story (which can be hard, because proverbially, every plan is excellent until it meets the players).

Sometimes they'll stage little or big events for players, e.g. if a player has let them know that he wants to kill a char, that is always a great opportunity for a neat send-off. Maybe the char is murdered during a banquet to make the other players aware of a treason subplot or he gets to save another character during a road robbery at the expense of his own life or something like that, that goes into the in game history books.