The biggest impediment to this happening is our overall acceptance of the outlawing of self-medication. If we legalize pot, or other 'recreational' drugs, how much sense does it make to restrict the purchase of all the other the medicines that currently require permission from a doctor (paying a premium to doctors and Big Pharma for the 'privilege') to get? This is what really scares them, that the corporations will lose their monopoly on the drug supply.
I don't agree with that.
Legalizing marijuana would appear as exactly what it is, the legalization of a primarily recreational substance which happens to have some medical usefulness but is not primarily a medication. More importantly and contrary to Reefer Madness propaganda, marijuana is essentially harmless. It is non-toxic and one cannot overdose on it, whereas the vast majority of prescription medications can effect serious harm if misused
The reason Big Pharma doesn't want marijuana legalized is it eventually will replace their most profitable product category, which is the broad variety of prescription tranquilizers. The fact is there is no better tranquilizer than marijuana. Its effect is superior to any other and it is not addictive or harmful to the liver.
The booze industry is also intimidated by the prospect of legal pot, which in time would seriously affect its bottom line. Marijuana is superior in every way to booze -- and it is harmless.