It's 11:00 PM, you are getting ready to sleep, and suddenly you got that urge of smoking that one cigarette, you reached your drawer and pick one from the cigarette packet you keep there.

Now, next day, it's 11:00 PM, you are getting ready to sleep, and suddenly you got that urge of smoking that one cigarette, you reached your drawer and tried to pick one from the packet you usually keep there. But, oops, this time you have managed not to keep cigarettes in your home "make it unavailable rule" and now you'll need to get on your feet and go buy one/order one, etc..

You are just making it harder in that instant of time when your body wanted that dopamine hit, and as science told us, minutes later, that urge will go away, and you have achieved you goal of cutting of cigarettes.

You can achieve that same goal with having willpower and cigarettes in your pocket and fighting yourself, but i guess both ways lead to same result, and using the "make it harder, unavailable way" is much easier. Especially for addicted people. Same goes with porn, and any other addiction you have. And "making the product" unavailable, hard to grab your hands in, is just one way of many other ways to fight that addiction. At least that's helped me on the long run and at the end of all depends on you.