Where do you get statistics on occasional/light illegal drug users who have no contact with law enforcement or mental health researchers? People with jobs and families have a lot more to lose by admitting to the wrong person that they sniffed $50 of coke at a party last weekend than by admitting they chugged $50 of booze and almost choked on their own vomit (for example).
Great points, and much more succinct than mine below.
I think your point is exactly what I mean about romanticizing alcohol. People practically brag about how hungover they are, or how much they drank. Shared misery.