Drug Cazer Walters said pot was indeed their big money maker:
$14 Billion In Annual U.S. Drug Purchases Via Mexico: Drug Czar
-snip-
Walters called pot the "bread and butter," "the center of gravity" for Mexican drug cartels that every year smuggle tons of it through the porous U.S.-Mexico border. Of the $13.8 billion that Americans contributed to Mexican drug traffickers in 2004-05, about 62 percent, or $8.6 billion, comes from marijuana consumption.
http://www.thecrimereport.org/share-post/14-billion-in-annual-us-drug-purchases-via-mexico-drug-czar
Though HIGHLY lucrative - there is far more money in other illicit drugs that are far more dangerous that resources could be moved to.
There is no drug shortage anywhere that I've heard of. Anyone who wants the more dangerous drugs can get them at a reasonable price. If demand is already being met, then moving resources to increase the supply doesn't help your profits.
er... “Czar”
That is only one drug czar in mexico. I guarantee you that 14 billion is NOTHING to the cocaine cartels.