There is no reason why a Human Greatweapon Fighter couldn't start out with Bastard Sword and Weapon Focus.
Reasons why a Human Fighter would take other feats:
-Is using a weapon that's not a sword. Particularly if using a different weapon is part of the character concept or their plan for later levels. Possibly going the Hammer Rhythm route or using a reach weapon. (Reach weapons aren't great on a fighter, but they still might choose to do so.)
-Is using his feats for something that makes him better at his role - defending the other PCs - and not something that makes him do more damage, which is the Striker's role.
-Spent his feats on Action Surge and Human Perseverance, because they're the two best Heroic Tier feats anyway.
-Really wanted Plate armor.
-Was given a free magical Greatsword with a cool enchantment on it by the GM at character creation.
-Wanted to Multiclass from the start.
-Has a pet Horse, wanted the Mounted Combat feat to match. (Note that Mounts are very good for Defenders, as it increases the defender's space to large. Now twelve people can be adjacent to you and suffer Combat Challenge and Close Burst 1 attacks, instead of just 8.)
Basically, spending two feats on one job is not exactly a no-brainer decision. There are other feats worth taking that aren't about your weapon damage.