That is an opinion that isn’t supported by any facts. Perhaps you could explain why a prohibition on alcohol required a constitutional amendment and prohibition of other drugs does not. You could demonstrate your amazing intellectual skills and knowledge in doing so.
Don’t expect an answer. Prohibitionists never bother to recognize their previous failed experiment.
Anyone who claims to be a conservative and favors the Drug War is shallow in the extreme, with little if any regard for either the constitution or individual rights. Common sense doesn’t really register for those people either.
Because people realized that people who want to fulfill their own selfish desires are going to do it (drink alcohol and/or smoke pot), anyhow, anyway. So, they didn’t pass the law to prohibit drugs. That is what YOU and others are, selfish, who support legalization of pot.