A PnP RPG doesn't need to have a GM-driven "plot". It can all be whatever the players want it to be. It just takes a great GM to run such a game. We've had those, and they were amazing. We've also had games that had absolutely no GM whatsoever. We've also played games that had absolutely no rules whatsoever. Sometimes shit didn't quite work as planned, but most of the time it was great.
I guess you get me wrong, i am such a GM. The way to do it have decent NPC's with their own goals, things that progress with or without player involvement. Thats the plot i am talking about , not forcing player in to that plot.
You might be just a person that living his life, but if world war 3 starts, your live will be effected, that doesnt mean GM should force you join the navy or be a general, and player shouldnt complain about not being able to affect the outcome if he had chosen to be involved. Or if you are a gotham citizen in Dark Knight Rises, you will be affected by the plot, no mater what you chose to do.
All i am saying there should be something going in the background , something interesting, and you should chose to get involved with it or ignore it. Either way you should be faced with the concequences.
Now with out a gm, with out rules, and just with the concept of the characters you are playing , you can play hours just with players with good RP skills. We sometimes let out gm go to sleep and continue our ingame discussion. But that doesnt work on Video games, or even in most PnP games without proper players. That kind of quality players are hard to find.
And while doing these, as a GM , if you feel that your players are feeling lost , without knowing what to do, but wanting to do something, then you have to intervene, before game becomes boring for them. In a PnP game , most important thing is your players. Its not intervention to rail them back to the plot, its intervention to guide them back to the fun. There is a huge difference between them.
Thats why, one of the most hard gametypes to pull of is sandbox RPG because , a player should have a freedom, but shouldnt feel lost while playing your vast world.
PS: I never said GM driven plot. It is an NPC driven Plot that you need the game to feel alive. If your NPC's dont have goals, plots, ideas of themselfs, they are just stats and they dull the game as a whole. The huge but subtile difference between a GM-Driven Plot, and NPC Driven plot is how the game will feel when playing.