The virtual worlds created with MUD software are dramaturgically and socially rich, and MUD players have been able to device means of communicating social context cues through the textual medium. For example gaming in some game centred MUDs focus more or less on only killing mobiles, monster that game controls and gaining experience points. Some ways of playing tabletop role-playing games don't differ at all from that. Social codes of some MUD demand role-playing when interacting with other characters. Mechanics of MUDs offer possibilities to be somebody else, not just play somebody else.
MUDs blur the boundaries between self and game, self and role, self and simulations.
But people don't just become who they play, they play who they are or who they want to be or who they don't want to be. Players sometimes talk about their real selves as composite of their character and sometimes talk about their screen personae as means for working on their real live lives. Therefore social interaction and role-playing can be used to make computer games more interesting and appealing. Note that not every good game needs those but as described earlier, game designers have successfully used this tactics in creating MUDs that has attracted players a long time. MUDs still attract new players despite the fact that they are basically same kind of game as first introduced in 1979.