Nothing exists in isolation. Thunderbirds, like everything else, was a product of its time. In the 60s everyone smoked. Offering someone a light or one of your ciggies was seen as an an acceptable way of breaking the ice, as much as asking what team you supported. It was a social skill back then.
My parents smoked, most adults I knew smoked. Ashtrays were common things found in most households. Having the technology to make their characters smoke must have seemed a good way for the Thunderbirds production team to make them seem more natural and human at that time. They might have had the imagination to devise future technology for the 2060s but they couldn't have forecast the way social trends such as smoking would go. I don't recall any specific product placement of brands in the programmes.
Us kids must have been passive smokers for years before we got to make a choice about it. I never took up smoking beyond some experimentation as a young adult -I just didn't like it. Come to think of it, I wasn't too fussed about football either. No wonder I'm such an unsociable git. I did like Thunderbirds though, Fireball XL5, Supercar, Four Feather Falls. Joe 90, not so much. I suppose that I was at just the right age to appreciate them when they appeared on TV.