Nicotine is addictive. More than heroin. Cigarettes, cigars, vapes, and even stop smoking patches, are ALL vehicles for delivering nicotine into the body. The media, and campaigns by tobacco companies, have all tried to make nicotine addiction seem normal. There are few if any actual, successful systems to stop smoking, except "cold turkey". Tapering off and nicotine substituting patches, just prolong the addiction. For someone to stop smoking, they have to really WANT to stop, and then they must put out great effort, to overcome the desire, from the addiction. Even after you stop, for a prolonged period of time, you are still addicted! The desire is great, and even ONE puff, will bring the addiction back 100%. Give your parents all the support you can. Don't criticize. There really isn't much you can do. Good luck!
Quit after 3 packs a day for 35 years