It's just part of their culture, you see. They'd prefer they grow watermelons, but hey, they want to grow opium. Never mind that the Taliban banned opium prior to our invasion, and never mind that 8 years after our invasion Afghanistan now has the global opium market cornered (over 95%). That's just uhhh an unfortunate coincidence to our invasion. This band of goat herders - the Taliban - whose armored vehicles consisted of beat up Toyota trucks, were capable of subduing the entire country, including eliminating the drug trade, but the most powerful military in the history of mankind not only can't burn the opium fields (although it certainly excels in slaughtering civilians), they can't defeat the Taliban either. Nothing out of the ordinary here at all. Oh, by the way - the president's brother, a prominent Afghan drug lord, is on the CIA payroll.