... don't understand why anyone does it.

There IS a reward for smoking besides the nicotine addictive demand. There is a pleasure one gets from the warmth of the hot smoke and the caress it gives to the interior of the lungs. Other than that, the nicotine withdrawal symptoms force the smoker to return to that slight reward they get.

I used to smoke a lot but quit... (counting....) about 40 years ago. (God, I'm getting old.) I abhor the smell of cigarette smoke now. It nauseates me. Cigar smoke is thousands of times worse than cigarettes and I never smoked a cigar. I don't just hate cigar smoke, I want to find a gun and terminate the cigar smoker. (What's worse than "hate"?)