"The government is letting you use some drugs but not others. Why?"
Because we let them. We have become such subdued and obedient little slaves that we would never ever dare to question or challenge government authority, even when they deny us, through force, access to nature, cannabis is a plant after all.
We really need to wake up and overhaul the system, even limited government is pretty dodgy IMO and the fact that we live in a dictatorship and only a handful of people can see it is quite disconcerting to say the least.
But to answer your question more directly, the masters have ALWAYS allowed their slaves to have some respite from their labour. In ancient Egypt the Egyptian rulers allowed their Jewish slaves to have beer. It kept them (mostly) placated and dulled the urge to rebel, just like it does today. That's why they 'let' you ('let' cos you treat them like your lord and masters)have some diversions, but not too many else you might become too relaxed and stop being a good and productive worker bee.
