membership cards

I noticed that a lot of the department stores are now giving membership cards to their customers. These cards will be giving the customers rewards for the frequency of their purchases at a certain establishment. It provides incentives and motivation to the customers to make purchases more to the said establishment. With these cards, it can also increase the sales of the business. Hence, the effect of these cards to both the customers and business is two-way. Not only the customer can gain rewards but also the business will gain more sales.