It's a basic rule in rpg : use your consumables, use your special spells, because if not you will never use them at all.
Source points are not here because they are needed, they are here because you can cast op spells with them.
Fane double turn spell / special summons / aoe spells of doom...
Not using source spells is pretty meh.
You are so right.
I have played many RPGs and in many cases my inventory was filled with tons of items I have never used because "I might need it later", well I never did.
There are games that have consumable items that you should keep for very hard bosses, like some games have only a few potions that give full HP and MP or that revieve you with full health. But D:OS is not one of them. You can craft or find tons of everything all the time.
Now comes the hardest part for me. To actually listen to your advice and stop hording items. Some habits are hard to change.
Prof. Dr. Dr. Mad S. Tist 
