Even though I am not an alcoholic or a hard smoker, I have some excuses or reasons for people drink and smoke as follows.
If people are not drunk or smoke a pack of cigarette at one time, I think the reason they drink or smoke is that they just want to try the tasty wine or relax and enjoy the life. Sometimes you feel so weird if a delicious meal goes without a glass of wine and it must disappoint you when you attend a party, they do not serve you any cocktails. Life suffered, so smoke or drink may play a role like massage to make adults relax from big stress.
The best reason or excuse for smoking and drinking may be that can make one feel like escape from the current life temperately. When you get drunk, you will not remember things you did, the words you said or even worst, you felt asleep and fall down immediately. Therefore, this is a perfect way to forget things shortly and a perfect excuse to smoke and drink.
Sometimes we can not blame people who smoke or drink because they may have no friend to talk to or things are not allowed to be discussed. What should they do? The only choice for them may be light on the cigarette, and thinking at the same time or talk to the wine and glass while drinking.
I can think many reasons for drinking and smoking. However, if you be yourself and not beyond the normal standard of smoking and drinking, any reason may be a good reason.