The same could be said of alcohol, but I doubt most people who are drinking are also driving while under the influence.
It’s absurd to think that most people who do other types of drugs are willing to drive while intoxicated while they aren’t while drunk.
My personal experiences in high school and college lead me to believe a lot of people think it’s ok to smoke and drive and to some extent do other things. While they will avoid drunk driving just because it’s much easier to detect alcohol.