Can someone give me a reason WHY item/weapon/armor durability exists?
One game that springs to mind that I've played recently with item durability is Dark Souls. The thing is, the price of repairing your stuff if you kept at least an eye on your equipment is pretty trivial. Killing a single Hollow Soldier is enough to fully restore weapons and armor for the most part. Honestly, I can see Dark Souls play the same even if the "feature" wasn't present.