Are you telling me, it's not already as we speak a giant waste of time and resources?
of course it is. and you're right, you shouldn't take my use of the word 'turn' to imply that staying in afghanistan can somehow make the entire enterprise a worthwhile one for the american taxpayer. nothing can make that so. the whole operation, even when the coin strategy was being marketed as a success a few years ago, has been a fiscal sinkhole without much hope for real victory. but it's not been a complete waste of time for everybody... the fact that along with iraq it basically surrounds iran makes it incredibly important given the current thrust of american foreign policy and israeli posturing. and additionally its a buffer against an increasingly hostile pakistan.
i don't really know enough to give a real list of institutions that have benefited from the continuation of the war but if its still going on, my position is that it's clearly in the interest of somebody. pentagon, high tech industry, the increasingly global cia, etc. the usual suspects. vague yeah, but that's my alternative position to your belief that two presidents have only refused to withdraw for fear of appearing on the world stage with their tail between their legs. my point is that for those with vested interests in continuing military presence in afghanistan, a complete abandonment would make all those years and all that money 'a waste'. whereas it's already a waste for the american taxpayer.