People that smoke don't care about those ads or warnings...they want cigarettes anyway and if a shop doesn't have them they will go somewhere that does have them and then the shop loses a customer which reduces the shops profits...
Take a convenience store for an example.....
they sell gas, deli foods, groceries, baked goods, coffee, cigarettes, cigars, chewing tobacco, sodas and all kinds of other stuff someone may need on the way to or from work or close to their house ect.
Now say I smoke cigarettes and the convenience store that I stopped at everyday to buy my coffee, my breakfast sandwich, my newspaper, soda for my lunch and my pack of cigarettes decides not to sell cigarettes anymore...
That means I would have to stop somewhere else to buy my cigarettes and if that place also has coffee, breakfast sandwiches, newspapers and soda then that store would get all my business and the other store that has no cigarettes would lose all my business.
It wouldnt be convenient for me to stop at 2 stores to get what I want when I can just stop at one that has everything.