I guess you could use the same explanation for meth, cocaine, heroin, kiddie porn etc etc etc
Still wouldn’t make sense.
The Founders had the wisdom to leave those decisions to state governments rather than federal. You should inform yourself on the expansive Commerce Clause and Tenth Amendment. It explains why fedgov runs health care, education, the environment and just about everything else. It's all in Obama's hands now.
But who cares about fedgov overstepping their constitutional bounds, right?