Because people actually care about the story in this game? People get really salty in mmos when they can't see the full story, especially when said story is a continuation of 1.0. Coil/Alexander actually have some amount of story to them also, Ozma had nothing.
What about the end boss of that 100 floor basement in Bevelle in FFX-2 which is required to unlock the 100% ending? That's an example of story being blocked by a difficult boss.