That’s like saying when you drive a car dangerously you’re only putting yourself in danger. When you smoke, yes, you are harming yourself, but you’re also harming others around you.
How’s that? Well, when people breathe in smoke (from the end of your cigarette or your exhaled breath) it is known as passive smoking or second hand smoke. By smoking around people you are exposing them to unfiltered smoke and thousands of harmful chemicals which could lead to asthma attacks, frequent coughs and respiratory illnesses such as pneumonia or bronchitis. Some non-smokers have developed lung cancer and died as a result of people smoking around them.
Check out second hand smoke for more information.