Most of these things are coping mechanisms, that we use to deal with living lives structured in ways that are bad for people. The 9:00 to 5:00 5-day work week is bad for you, but weed and cigarettes and caffeine and alcohol help you to keep doing it day after day. That helps the soften the physical pain, or to help you relax after a particularly bad shift, etc.
I disagree with the statement that sugar and gluten are bad for you, but at least in the US they do have excessive amounts of it into everything.
One other thing is that I think it’s bad to lump all drugs into the category of saying it’s bad for you, because every drug is different and the way they affect you varies dramatically. It’s important to evaluate drugs individually - remember that the medication that you get at the pharmacy are drugs too.