Booze is more respectable than pot so it's natural there would be more cases of use. One thing is alcohol isnt a gateway to heroin use like marijuana.
You can buy alcohol legally in a store, where there is no heroin.
(Where it's still illegal) Marijuana is bought from a drug dealer (no, not a pharmaceutical company), where most of the time you can also buy heroin.
I wonder why some claim that marijuana is a gateway to other harder drugs.
Having been around both alcohol and marijuana for over 20 years, my experience has been that alcohol is far, far more damaging than marijuana.