The best explanation I could find (in a hurry) was at the Marginal Revolution blog. Here goes:
The bootleggers like prohibition because it gets rid of competitors. But a politican who wants to listen to the bootleggers (and preserve their business) needs a more high-minded cause to sell to the public. The Baptists give the politicians cover with the argument that drink is from the devil—it leads to social unrest, unemployment, higher social costs and so on. Same with Mexican trucks. Who can justify keeping out lower cost Mexican trucks just to keep the wages of Teamsters high? Enter Public Citizen (a political watchdog group). This isn’t about greed. It’s about keeping American air clean.This is one of the reasons why the insurance companies aren't wailing and slashing their collective wrists over Obamacare. It's going to make it almost impossible for a new competitor to enter the market. The insurance companies, in this case, are the bootleggers.
This is why I can't go to the former Army medic down the street for prescription drugs. The AMA fits the role of "bootlegger" nicely.
Now go here. Get back to me when you finish. You can tell who the bootleggers are, right?
It's for The Children. It's for The Air. It's for Working Families. Naaaaaaw. It's almost always for The Bootleggers.
Don't be fooled again.