Probably because they were wise puffs, rather than stupid puffs.
My mother smoked until I was 14. My grandparents smoked, almost everyone smoked. They smoked everywhere, at home, at the table, in the hospital, etc.
This was during a time when the famous Surgeon General’s Report on smoking first came out, and there was lots of pressure from the children to the adults to give up smoking.
Most did. As I said before, everyone who didn’t have a severe and unbearable physical urge gave up smoking over the next 20 years. What sane person wouldn’t do that if he could?
I tried it, because, that’s what teenagers do, I suppose. I had to confirm it wasn’t for me, even though I probably knew that already.