My brother continued to smoke after lung cancer surgery, and my wife's stepmother kept on smoking until the day she died of lung/brain cancer. Neither lived to age 70.
For many people it's nearly impossible to quit smoking, there are apparently some genetic factors that impact nicotine addiction. Vaping is apparently almost as hard to quit and might lead to some medical conditions that are worse than those caused by smoking.
What worries me most about the creeping decriminalization of marijuana is that the research is starting to show marijuana smoke has many of the same toxic substances as tobacco smoke, and that doesn't take into effect what THC does to the body and mind over time. (But the long term effects of alcohol use have been known for a long time, and alcohol has been around for millennia.)
