There is a very substantial difference between legalizing pot and legalizing all drugs. And I doubt that everything would just change overnight. The whole idea is to control and tax the substances. That would make it safer for the user and give the government more money for schools, weapons, and world domination.
It is a pretty common belief that putting resources into enforcing anti-marijuana laws is just plain silly, and I tend to agree. There are much larger issues that should be focused on.