I have no problem at all leaving smokers to smoke - as long as they pay for their own medical insurance like I did as a smoker Yes you can choose to smoke, or eat way too much sugar, or drink 20 pints a night, or parachute out of a plane, or keep poisonous spiders as pets, or take a toaster into the bath - Just don't expect me to f***ing pay for it when it all goes wrong!
You forgot to mention all the people who overindulge in alcohol. who eat a poor diet, overweight, don't exercise, ignore safety protection on construction sites, economise on car servicing, couch potatoes, have too many children, drive carelessly ...
It's not a perfect society we live in. People are not perfect and make mistakes. Out of the money spent on UK healthcare, a vast amount of the cash goes to pharmaceutical companies who undoubtedly benefit far more from this than do NHS patients.