Beer, wine, tobacco, and distilled spirits are exempt from the Controlled Substances Act.

I'm sure there are many reasons for that being the case. I'm also sure many of those reasons are disputed by the pro-drug lobby. There is plenty out there on both sides of the argument.

Even though alcohol has a potential for abuse, it also is societally accepted and can be used without the purpose of specifically obtaining a high.

The reason is not specifically clear and is open to much interpretation.

Caffeine is considered a psychoactive drug and is also not on the list.

DEA Drug Scheduling is here.....

http://www.usdoj.gov/dea/pubs/scheduling.html

EDIT: Alcohol is still prohibited in some places around the country because of local laws.

I'm sure many people have been on a road trip and wound up in a "dry county" at some time or another.