I think that, unlike all other lore and side quests, the MSQ informs "current events" in the world. This is happening now. And while not all is pertinent to RP, there are some events in the MSQ which have wide, rippling effects on the world.
These things are all part of the MSQ, and whether we choose to RP characters experiencing these events first hand or not, these events affect the world at large and the setting in which we RP. A year ago, probably no one in Ul'dah or Gridania had ever even heard of a place called "Doma." (Limsa maybe cuz they trade with everyone in the world.) Now its almost common to meet Doman RPers.
These things are all part of the MSQ, and whether we choose to RP characters experiencing these events first hand or not, these events affect the world at large and the setting in which we RP. A year ago, probably no one in Ul'dah or Gridania had ever even heard of a place called "Doma." (Limsa maybe cuz they trade with everyone in the world.) Now its almost common to meet Doman RPers.