You can build something people want and which is bad for health, they're not mutually exclusive. People commonly want things that are linked to negative health

You can build something people want and which is bad for health, they're not mutually exclusive. People commonly want things that are linked to negative health outcomes: alcohol, sugar, fast food, lack of physical activity, working a high stress job, living in a city, watching the news, etc. Personally, I take the position that people best know what's good for them because I don't see good alternatives to that.