I've been discussing the merits of various roleplaying systems with my friends of late, particularly the two different styles of roleplaying that seem to predominate the market today. These are, to write it in a reductive shorthand, storytelling styles and gaming styles. Now, while I do believe that GNS theory has a lot to offer to the discussion, let's put it aside for this argument. We can pretend, you and I, that the words "story" and "game" have no weight or semantic baggage and evaluate them from first principles.
I would argue that one of the important elements that makes roleplaying games fun is surprise. Responding to surprise is a piece of the puzzle that is almost integral for me. If the game has no surprise, I don't see the point in playing it. If I have already plotted out every move like a master chess-player and nothing deviates from my plan, I am bored. Stillness, as they say, is death. Movement, strife, is life.
What does surprise have to do with these two divisions of game-type? Well, let's delve into exactly what I mean by story and game focused roleplaying. Story-focused roleplaying aims to give as much creative freedom as possible to the player. If you want to play a grizzled old man, you should be allowed to! After all, this is your game and your imagination. A fair point; however, this brings story-based roleplaying into conflict with many rules systems. How could you realistically portray a grizzled old man in a way that was fair to the other players? Is he very high level, or very well-lanned? That will be a problem for the rest of the group. It's rare, I find, for people to want to play old men that have no useful combat skills (powerful magic, a veteran's life of war and swordsmanship, etc.) How can we make the rules accommodate both the grizzled veteran and the fresh-faced young novice? The answer is simple: we can't. At least, not in any way that will remain fair and keep everyone on board.
The solution that many see is simply to do away with the rules. This is freeform roleplaying, the most story-focused type of roleplaying that there is. In freeform roleplaying games you generally begin as a character with a storied history. This history informs every action that they make. However, since there is no resolution mechanic, whenever you interact with someone else you two (or three, etc.) must come to an understanding as PLAYERS about what your CHARACTERS will do. This, for me, kills the element of surprise. It transforms a game where you pretend to be someone you aren't into a collective playwriting experience where you are an actor, director, writer, and audience balled up into one. I find little joy in this! That's not to say that roleplaying in freeform is bad, it is just inherently predictable and tends to be static.
What do I mean by static? Well, most players don't want changes to occur to their own character without their say-so. The character is a form of sovereign territory, and it's human nature to be possessive about what you perceive of as yours. (Nevermind that in the metaphorical language of freeform characters should actually belong to everyone and adapt with the circumstances and the narrative need, since the "game" is really an act of collective storytelling—as soon as someone is threatened with death or maiming they will instantly respond with "nuh uh!") That is one form of statis that plagues freeform roleplaying.
The other is something I like to refer to as background weight. Because characters created for freeform tend to have long and involved background stories, everything important has already happened to them. Their backstories are like an anchor that prevents them from sailing too far afield from where they were anchored. Indeed, the lengthier the background the more likely that the player will feel as though they must talk about it. This creates pontificating characters who expound or discuss all the great things they did once upon a time but avoid doing anything new for fear of running into the situation above and injuring some other player's sense of autonomy.
How are these things solved, then, in games that have conflict resolution mechanics? The first should be obvious: surprise is maintained by the element of randomness in the game. Did you hit that guy with your sword? What jumped out of the other room? This is bolstered by the presence of a referee who can guide the actions of the non-player characters.
Stasis is blocked because player autonomy is nil in game-based roleplaying. Players can try to do something, but there are no guarantees that it will succeed. Players are not autonomous, they are bound to the strictures of logic, the setting, and the referee. While players in freeform may willingly bind themselves to these rules, the very lack of an overarching force means you cannot expect it of them.
Background-weight is countered (at least in AD&D) because everyone who rolls up a new character starts as a young person with little experience. Instead of talking ad infinitum about their accomplishments, they are encouraged to go out and accomplish. The sense of action moves from the past to the immediate. When you play D&D you are in the now.