This is why!
Remember....You asked!!
While there is no federal law prohibiting open containers in a motor vehicle (and both the 21st Amendment and the Commerce Clause of the Constitution of the United States likely would prohibit the United States Congress from passing such a law), the
Transportation Equity Act for the 21st Century (often referred to as "TEA-21"), which Congress passed in 1999, created incentives for states to comply with certain federal requirements. Any state not in compliance has a percentage of its highway funds transferred instead each year to alcohol education funding. This is a similar approach to that which Congress took in 1984 when it passed the National Minimum Drinking Age Act, which successfully sought to get all states to adopt a legal drinking age of 21. TEA-21 has not met with the same success, as some states, like Missouri, openly refuse to implement new laws to meet its requirements.
To comply with TEA-21, a state's motor vehicle open container laws must:
Prohibit both possession of any open alcoholic beverage container and consumption of any alcoholic beverage;
Cover the passenger area of any motor vehicle, including unlocked glove compartments and any other areas of the vehicle that are readily accessible to the driver or passengers while in their seats;
Apply to all open alcoholic beverage containers and all alcoholic beverages, including beer, wine, and spirits that contain one-half of one percent or more of alcohol by volume;
Apply to all vehicle occupants except for passengers of vehicles designed, maintained or used primarily for the transportation of people for compensation (such as buses, taxi cabs, and limousines) or the living quarters of motor homes;
Apply to all vehicles on a public highway or the right-of-way (i.e. on the shoulder) of a public highway;
Require primary enforcement of the law, rather than requiring probable cause that another violation had been committed before allowing enforcement of the open container law.
Currently, 39 states and the District of Columbia are in compliance. Alaska, Louisiana, Tennessee, and Wyoming have similar limits on the possession of open containers in vehicles, but not to the level of TEA-21 compliance.
As of November, 2007, only one state (Mississippi) allows drivers to consume alcohol while driving (as long as the driver stays below the 0.08% blood alcohol content limit for drunk driving), and only eight states (Arkansas, Connecticut, Delaware, Mississippi, Missouri, Tennessee, Virginia, and West Virginia) allow passengers to consume alcohol while the vehicle is in motion. Still, local laws in these states may limit open containers in vehicles, although those local laws do not impact the state's compliance or noncompliance with TEA-21.
Hope you enjoyed!
JIM