In my opinion, recreational marijuana use by adults in the workforce is in many ways a harmless and victimless activity. It does not cause hangovers and missed work, it is not addictive, and it does not inflate health insurance premiums for replacment organs, such as healthy livers.
Perhaps, except for "short term memory loss" associated with smoking cannabis.
I would think short term memory loss (persistent as the drug remains in the body for some days/weeks) could be an issue if you are a surgeon, airline pilot, stock broker, etc. where decisions must be quick, clear, and accurate.