As a former smoker and current person above their ideal weight who goes to the gym and studies less than they ideally would all of those things are down to prioritises.

Nicotine is fantastic, like caffeine and alcohol, running or weightlifting. Sometimes you have other priorities and you give up something pleasant because it has bad consequences.

Vaping is nicer and safer than smoking, which I would not recommend anyone start, for the wretched smell alone never mind the health effects. If I ever feel like nicotine again I’ll buy a vape again.

I do believe most smokers today are troubled by something, yes. In the past, it was culturally acceptable but not so much anymore (especially in Northern Europe, I can't really talk for the US). Most people who are bothered by something have a sort obsessive habit, e.g shaking one leg or a finger, touching his hair, smoking, chewing something, eating salty or sugary things. Just an observation.