Demos spread the word about the game, especially when you have 5 demos that are released over a period of time. It works as advertisement. There were also TV commercial for it i think.
No one says that there was no marketing, but it´s funny that the damage control reached the level that now Bravely Default suddenly became a title with a comparable marketing budget to SS only because it sold more than Soul Sacrifice in its first week. BD even had shortages due to a low first shipment.