Video Game Logic - The tragedy of loss...in a universe of Phoenix Downs and whatnots...

they dont use items because the plot demands it.

…Youre looking WAY to deep into this, pal.
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Its a gameplay design, it doesnt have to be connected to the plot (at least, not "directly"), if so, that would mean that EVERY game that uses healing items should not have a character dying, because they have those… that the player decides to use just to win a battle.
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I mean, seriously?