Why are we doing so badly out of war?

Why has USA pulled out of Afghanistan, but are still all over Iraq? They aren't that far apart, and both strategically very significant to the fight against terrorism?
Then it finally hit me. In Iraq, US firms have massive contracts rebuilding the country, paid for out of money from the oil that the country can sell. And in Afghanistan, the country is bankrupt so any work that needs doing is paid for by charities, who aren't known to give the contracts to friends of the government, nor to give lucrative contracts with very few targets or milestones.
At risk of being sued for libel, it seems that we did very badly (by this single measure) in Iraq - in spite of supporting US to invade and committing troops and lives, we didn't benefit from the bonanza of rebuilding contracts post-war. We did get some contracts, mostly subcontracts to do the work from US companies who won the main contract to take the profit.
Should we be more mercenary? Threaten to pull out of Afghanistan until the balance of reward is a little fairer? It isn't all about money, but as long as US presents it this way then there will be resentment, both in the occupied country (Iraqis seeing oil revenues scooped out of the country in the pockets of people they could view as friend or opressor - what will they think) and amongst the allies