every RPG has item restrictions, implementation differs according to its core rules.
D:OS has one of the variations, which Larian love. most loot heavy RPGs have character level as item requirement: you suppose to use more power items when you get to higher level.
don't drag "real world" sense into game core rules, we're in a world of void dragon and crazy wizard.
to your STR-weapon question: the game is telling you that if you're not serious about a fighter character, you don't deserve that lvl 20 sword:)
btw, don't like such game rules? mod it.
Last edited by teardropmina; 02/09/14 12:05 PM.