The potential benefit of having states within the United States is the competition it fosters. States with unproductive laws and policies tend to lose out to those with less unproductive laws and policies (note that I avoided any reference to states with productive laws and policies – there are none :-)).
The real purpose of the states’ attorneys’ general is to eliminate as much of the potential benefit from competition as possible.
The following is from the Wall Street Journal’s “Best of the Web Today - September 28, 2007” by James Taranto.
Life Imitates 'Seinfeld
"Newman learns that bottles and cans can be refunded for 10 cents in Michigan (as opposed to 5 cents in many other states). Kramer tells him it's impossible to gain a profit from depositing the bottles in Michigan due to the total gas, tollbooth and truck rental fees that would compile during the trip, but Newman tries to find a way."--Wikipedia description of "The Bottle Deposit, Part 1," aired May 2, 1996.
"Authorities said they arrested 10 people and seized more than $500,000 in cash after breaking up a smuggling ring that collected millions of beverage containers in other states and cashed them in for 10 cents apiece in Michigan."--WDIV-TV Web site (Detroit), Sept. 26, 2007.