"Why roll at all? Why not just agree on what's happening? We're all fair-minded adults, right? Well, social agreement is a fantastic ideal, but it is subject to bullying, blustering, intimidation, manipulation, cajoling, persuasion and lying: all things that are separate from the characters -- part of a social dynamic that is apart from the game. By relying on the dice, everyone is on a level playing field. Burning Wheel is a game, not acting class. The versus tests get everyone playing the game, and besides, your characters only advance if you roll the dice!"
There are multiple things here that I really dig. The quest for a game that works, even if people are not acting live fair-minded adults can take you down many different paths, but having a system is a must. Note also that BW is a game, and I think it should be emphasized. While you can go in a mental spin about how roleplaying is a new art form of interactive storytelling, it shines when it's grounded. A game. A game which can be played on multiple levels, at the same time be what different people want out of it. Finally, by grounding that in the rules, preferably the advancement rules, you have a vehicle carrying the kind of game play you want. There's nothing like it.
Roll the dice.