Why is our law system so soft on druggies?

I am sick and tired of seeing drug users not get jail time but 6 months of probation for getting caught smoking marijuana. These criminals are a threat to our society, and they should see a minimum of 5 years in prison for breaking the law. Marijuana is a harmful drug that causes psychosis and promotes a loser lifestyle. Why is it that our legal system is all about coddling these drug using criminals? Shouldn't there be a change?