The amount of people that smoke in America has declined over the past few decades. 40 years ago, as many as 40% of people smoked. Today less than 20% of people smoke nationwide. This means that the tobacco companies are making less money. If they want to keep their income up, they have to increase the prices of each pack of cigarettes.
Even though taxes keep the price of tobacco high, the price of packs themselves has gotten higher. It doesn't cost that much to make a pack of cigarettes, but the big tobacco companies are still slowly increasing the costs, on top of the taxes.