I mean, is there any reason to not equip everyone with the exact same weapon type?
Why give
Vaan a Dagger,
Basch a Sword,
Balthier a Gun...
...when you can just equip all 3 with the same high attack weapon? Most recently the most powerful weapon I could buy was a Javelin. Why wouldn't I just have all 3 members equip a Javelin instead of having each equip various weapons?