Like many things, it’s an irrational decision to start at some point, and then addiction keeps you doing it. I have tried out a few drugs in my teenage/young adult years, including some “hard” ones, which ended up genuinely being one-off curiosity things for me. But the one that I simply wasn’t able to kick until last year was nicotine. It really is scarily addictive for something so widespread and legal. (Alcohol was also hard, but easier for me).

That, and the part about “no high” is just not really true, even after you develop a dependency/addiction (with rapidly diminishing returns, of course). But especially when first starting to vape/smoke, there are very much effects beyond placebo. It hooks into a lot of your neurochemistry, and like most things that do, you feel that. To the point that, e.g., many people that consume weed with tobacco, will think the initial wooziness they feel is already due to the weed, when really, it is a tobacco hit. The weed effects generally come afterwards.

Of course, the effect is not at all as intense as alcohol or other drugs, but there are effects. There are also, to my knowledge, some indications, that a lot of people with ADHD use it to self-medicate, since it seems to affect them differently, like other drugs do, too.