On the battalion side, if a cadet does walk away, this leaves the 3 year scholarship locally, which can be re-awarded to those who truly chose "a different path." As mentioned above, the Cadre get a chance to try before they buy so to speak.
and common sense, its just plain cheaper for the Army. My battalion was mostly non-scholarship, as is most I assume. There were several in my commissioning class that started out not really knowing if the Army was the right fit for them, but ended up winning a scholarship and commission, a few were re-joining from other schools/battalions. Tons of dynamics, battalion size, zip code, social make-up, major, prior service, etc.