The problem is, you can rarely prove a person's illness is a result of their lifestyle, and that they definitely wouldn't have developed it had they lived a healthier lifestyle. As well as that, some people are far more susceptible to environmental factors influencing their health than others so it can be difficult to know how much of their health is down to genetics and how much is lifestyle. People who smoke and drink pay high levels of tax on those products, so they ultimately are paying more anyway.