People will play video games for days on end and not contribute to society, and could even been seen as "not functioning properly in life"...many people pushed for legalization because there are health benefits (non-addict pain relief, cancer fighting properties, seizure reduction....) - not because it is some cure all.

Ultimately the issues comes down to personal freedom. If you are not allowed to ingest something that does not cause pain or hardship on others...are we truly free?