Double heart bypass and on dialysis and is smoking again. Since dying, why not?

Indeed. If you are a competent adult you have exclusive homestead rights over your body. If you decide to continue to harm yourself, in full realiazation that doing so may hasten your demise, then it's on you. This is a charged question, bordering on assisted suicide concerns. Your doctor can rightfully disagree with you, & should, but ultimately it's your life - your decision.