Do you collect $2 bills? Do you know anyone that does? Odds are, you do. This is the problem.
The only two money-printing factories are in Fort Worth, Texas and Washington DC. The prints do not simpley print as much money as they want. They only print enough for a stable number of bills to enter the circulation. Appearently, people collect $2 bills because they think they're rare. That is both true and false. The $2 bills are rare because everyone saves them and does not put them into circulation (i.e. spending them). Because for this, the prints do not print as much as other bills are. So next time you save your $2 bill, REMEMBER: They're only rare because thats what everyone thinks.