Hello, your understanding should be wrong. People who don't smoke or drink are unhealthy because they may have been harmed by secondhand smoke. In fact, second-hand smoke is more harmful than smokers.
Suggestion:
Nicotine in tobacco can cause many diseases, including cancer. This doesn't mean that you will get sick after smoking. Comparatively speaking, the incidence rate is much higher than other people. Moderate drinking is good for health, but not excessive. It is suggested that from the health point of view, we must quit smoking and limit alcohol. For the health of yourself and others, please develop good living habits.