Alcoholics seem to function better in society than people that smoke dope every day. I have yet to make a traffic stop on a really nice car, in a really nice neighborhood on a person with a really nice job thats been smoking weed. Im sure there are some out there that do it but its not even close to the norm of weed smokers.
I'd be interested to see the stats on fatal crashes caused by someone that's drunk vs. someone that's stoned... Of course when you're only driving 20 mph I suppose that might influence the mortality rate of the crashes.