What is this psylocobin you speak of? I know nothing about it...
Actually they could allow pot for personal consumption. It would require a certification (kind of like prescription drugs) sticker on each 'container'. The sticker would cost 50$ per oz.
The main reason it will never likely be legalized is there is no real way to measure intoxication like a breathalizer or alcohol content in the blood stream. The ingredients of pot are very complex and they really can't break down how it affects people as individuals. Not to mention the active ingredient remains in the system well after the intoxication is gone.