I think this is addresed earlier in the post (?) but generally, the extraction cleans up the dose so you don't get stomach flips and gastro-intestinal discomfort. Also, the trip comes on faster and cleaner, more like a drug, less like an uncomfortable body-loaded entheogenic experience. It also does make storage and dosing easier.
Example: you and a buddy both snarf 2grams. You go through the roof, but for whatever reason your buddies' shrooms are weak and he doesn't have the same experience... the extraction makes the dosage standard so there's no variation among psilly ingested.
Straight shroom plain kills my stomach, and I tend to spend 1/2 the time thinking about life while sitting on the can
the extraction removes that completely and makes for a reliable, repeatable experience every time; the only variant being your mindset before ingestion.
hope that helps,
soliver