I think most will agree, substances, chemicals and such do effect people in a wide range of ways. Some may get away with a habit such as this, many won't and I have seen a bunch that succumbed to it. 2 come to mind right now, my neighbor who passed Feb 15th of this year, and a long time friend, neighbor, co-worker whose son is a long time great friend. Both of their demises were directly attributable to cigarette smoke. My neighbor on this lane, suffered from cardio problems directly caused by it. He just retired because of health reasons, just filed for social security, never got a dime of it. He had a pulmonary embolism at some point prior, so they had him on blood thinners, the sunday morning he passed, he had another event, dropped where he stood, opened up something and bled out on the floor, his wife came home from attending to her elderly mother to find him in a pool of blood. The other, had a respiratory event, he could not recover from, his wife called his son from work, paramedics, they watched him pass away, he did have a do not resuscitate order, that was that. Both his wife and son were devastated, but they knew it was inevitable. He was of the same cloth as you and likely your dad, he was a navy man, an extremely talented mechanic, body man who knew lead work, all the welding processes,and I mean all of them. He'd work in gasoline tankers, and knew all the old school techniques of body work. I worked with him for a local site contractor, he repaired heavy equipment and trucks and just about anything for that matter + the high end body work, and he was a talented artist, did all the hand painted lettering of trucks he could get, his abilities went far beyond what he exhibited. Pall Mall non filters were his brand, his last days were sitting in a chair, with a fish like expression on his face as he gasped for air. My last memory of him as I cut the grass across the road as he watched. Like you said, there had to be other factors, but the main one was cigarettes, as that was a constant in his life more than the different work he did. He owned a shop for many years but also did a lot of other things, but always smoked. He'd never stop for coffee when we were hauling, but sure as heck would to get a pack of smokes, telling me "don't tell my wife" she knew all along!
My point is, its playing roulette with your health, all the carcinogens, chemicals, now fire retardant, lets not forget polonium 210 which is interesting given its in modern cigarette tobacco and how that actually happens, really odd but it does. We cannot deny that whether its genetics that allows some to get away with it, or that even 2nd hand smoke sets the stage for pre-cancerous cells, there is NOTHING good about it, whether you can see it or its covered up.
One friend smokes sparingly, buys tobacco from a smoke shop, rolls his own, uses filters, but sometimes he does not. There is a distinct difference between commercially sold tobacco and what he smokes, you can smell the difference. I don't smoke, never did. On a rare occasion I do like a fine cigar, but even then it makes your mouth and tongue taste like it, like til the next day LOL! I rolled up what he smokes once, and smoked it like a cigar, not inhaling, it was enjoyable in that way, but I could not smoke a pack of those a day, week or month. Don't interest me, but I was surprised at the difference, being like a smooth cigar. No way I could even tolerate a commercial product, I honestly don't know how that is enjoyable. If you were to grow your own and process your own tobacco, tell me, (your dad would have to know) you can't even compare the 2 together can you? I would agree moderation is best, given most have an undesirable habit of some sort, what they sell is addicting and they've known of the consequences for 51 years or more by now. So being addictive, be it associated with commercial tobacco or just tobacco itself, there is no moderation, its excess and too much of anything is usually never a good thing. Information I've read about this states that 2nd hand smoke is harmful by each single exposure, its documented, people with this habit far exceed 2nd hand levels, daily for years and wonder why they become terminally ill ???
My mother smoked while pregnant, I was premature and underweight, who knows what else, she knew it was not good, her dad did the artwork for a cancer society campaign, he was a commercial artist for the state commerce department, he made stickers, skull with cigarettes as the cross bones, "cancer sticks" and its copyrighted to this day, what he created. He smoked like a feign, ended up with high blood pressure, a direct cause of smoking, he just retired and went on his first vacation, but did not take his meds, had a stroke, they found him on the kitchen floor, he lived another 6 years half paralyzed. I spent a childhood visiting him, first in the VA and then other places, then watched him pass. No sane mother to be would indulge in cigarettes or alcohol today. For every one that gets away with it, as I see things,(opinion LOL we all have one LOL !) several do not. Those kinds of odds speak for themselves. Sure I've known a few George Burns as well, they are rare though.