Beer in the combat zone

I read today in Army Times online,"American troops in Iraq will be allowed to drink beer without fear of court-martial for this year’s Super Bowl — an exception to a strict military ban on drinking alcohol in combat zones." I understand fully why alcohol is essentially banned in Iraq and Afghanistan, but it's interesting for me to compare how it was in Vietnam when we had way more alcohol than we needed (or should have had) and it was available at unbelievably low cost, compared to today's prices. Examples: a case of beer in 1966 was cheaper than a case of Coke, and a bottle of vodka or whiskey was around a dollar. Different world…different war.