In an article published by US National Library of Medicine
    National Institutes of Health, entitled 
Tobacco point‐of‐purchase promotion: examining tobacco industry documents, states, "Tobacco companies pay financial incentives to encourage 
retailer cooperation in three major areas: posting point‐of‐sale 
advertising and signage; providing point‐of‐sale product displays; and 
providing pricing and promotional incentives to consumers. According to the Federal Trade Commission's Cigarette Report for 2003,
 tobacco companies in the United States had a total combined advertising
 and promotional budget in excess of $15 billion in 2003, and the 
largest proportion of this spending was allocated to the retail setting.
 Tobacco companies allocated 1.1% ($165 million) to point‐of‐sale 
advertising and 8.1% ($1.2 billion) to promotional allowances for 
retailers (that is, to encourage retailers to carry specific brands as 
part of their product inventory and to encourage point‐of‐sale product 
displays of these brands). A whopping 71.4% ($10.8 billion) was 
allocated to retail price discounts. A further 4.5% ($677 million) was 
allocated to providing bonus cigarettes as part of retail‐value‐added 
promotions, and 0.1% ($20 million) was allocated to non‐cigarette 
bonuses as part of retail‐value‐added promotions. In total, this means 
that 85.2% of all advertising and promotional spending in 2003 was 
allocated to various types of incentives at the retail level (compared 
to only 65.6% of the $5.6 billion expenditure in 1997).
In
 order to secure prime display space for a product, it is a relatively 
common marketing practice among all types of manufacturers to pay 
slotting allowances or slotting fees to retailers.
 Tobacco companies engage heavily in this practice and commonly pay 
slotting allowances or slotting fees in order to obtain preferred 
point‐of‐sale display space in retail stores, more enticing displays, 
and more competitive retail prices.
Several
 studies have examined the use of tobacco point‐of‐sale ads and displays
 at the retail level in the United States, and have found both 
advertising and product displays to be highly prevalent. In a 1991 study
 of 61 stores in Buffalo, New York, the average number of product 
displays varied from 4.3 per store for privately owned grocery stores to
 7.8 per store for chain convenience stores selling gasoline.
 A state‐wide study of 590 stores in California in 2001 found that 85% 
of all product displays were within 4 feet of the checkout counter and 
11% of all stores had exterior signs that exceeded the size limit 
specified under the Master Settlement Agreement (MSA). A Massachusetts study found a shift toward signage on retail exteriors after the MSA.
 A study of 3462 stores across the United States found significant 
increases in the use of tobacco advertising both inside and outside of 
retail stores in 1999, when compared to the situation before the MSA 
implementation of the billboard tobacco advertising ban, indicating that
 point‐of‐sale advertising had grown in importance.
Given
 the large number of people that have intentions to quit, retail outlets
 may provide a means for tobacco companies to provide timely product 
purchase cues to would‐be quitters. Consequently, the retail setting may
 present relapse challenges for quitters.
 This suggests that the point‐of‐sale environment may be important to 
tobacco companies as a means of reaching would‐be quitters with a 
tempting reminder.Several studies have found that cigarette point‐of‐sale advertising and marketing materials are more prevalent in stores where adolescents shop frequently. Youth who are “experimenters” with tobacco are more likely than other youth to report exposure to tobacco marketing in stores. The use of self‐service tobacco displays appears to increase youth access to tobacco, both through shoplifting and through illegal sales to youth. The type of cigarette advertising found at the point‐of‐sale has the potential to influence adolescents to view users of particular cigarette brands in a more favorable light. This suggests that the point‐of‐sale environment presents a place where youth are exposed to tobacco marketing to a significant and influential degree." (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2563651/)
In fact Phillip Morris' website, they offer intensives "Retail Leaders is a merchandising program that is designed to create retailer alignment with PM USA by offering incentives to best present our brands to adult smokers. Retail Leaders is developed on the following category management principles, each of which is designed to help retailers best meet the preferences of adult cigarette smokers:
- Present PM USA’s brands in the best positions
 - Allocate merchandising space according to the company’s share
 - Clearly communicate price and promotional offers
 - Prevent cigarette access to underage purchasers
 
Our trade program has a variety of merchandising options for retailers to choose from. These options are designed to offer retailers flexible choices to best meet the needs of each store. Retail Leaders includes several features to help prevent underage access to tobacco products and to manage the category in a responsible manner. The Food and Drug Administration regulates the marketing and sale of cigarettes at retail, including requiring retailers to merchandise cigarettes in a non-self-service manner.
However, in addition to requiring that retailers comply with applicable laws and regulations, the Retail Leaders program also requires retailers to take additional measures that are not mandated by federal law, including:
- training store personnel who sell tobacco products using We Card® or equivalent training;
 - displaying We Card or equivalent signage;
 - using an age verification tool;
 - placing retail signage that tells adults not to buy tobacco products for kids; and
 - adhering to the Master Settlement Agreement.
 
To encourage retailers to take further responsible retailing measures, we offer additional financial incentives to retailers who refrain from placing any cigarettes, cigarette signs or brand imagery associated with cigarettes on top of or below the front of the selling counter that is closest or in front of the primary location in which cigarettes are merchandised. The Retail Leaders Program also includes limits on the location, size and the amount of PM USA interior and exterior signs at retail." (http://www.philipmorrisusa.com/en/cms/Products/Cigarettes/Marketing_Sales/Retail_Stores/default.aspx)
Despite all of that, I don't think if a product sells, at all, not one tin, pack, etc, it is just taking up space on retailers' shelves.