Bard is easily the most important human character in a story almost entirely about non-humans, and even though hes not introduced until late in the game, he plays a huge role in both the conflict with the dragon and the events that follow. The film-makers need to establish not just his place in the society of Laketown (the human port on the Long Lake south of the Lonely Mountain) and his skills with the bow, but they also have to fit in small-but-important details like his ability to talk to birds (no, really).
It's relatively brief compared to the other sections of the Silmarillion, but no less epic.
