Why not? In part, because the agreement requires standards that might not work in the state's favor. For instance, Maryland's current sales tax rounds up while the other states favor rounding down — a seemingly trivial difference that can add up to millions of dollars. Maryland's recently-enacted 9 percent sales tax on alcohol is a problem, too, as the agreement calls for a single tax rate (not necessarily the same rate as other states but one that's not variable from product to product). Even so, the agreement would require the blessing of Congress, which remains unlikely.