Because the first consideration in any marketing activity is to define the most likely customers. The more precisely a business can define its target market the better it will be able to aim mailings to this audience. As a result, it will receive better response rates. Mail lists can be created internally or through list rental. The least expensive list would be one the company creates on its own through its existing customer database or through resources such as the yellow pages or Hanes Directory.
People move, businesses go out of business, move, or have new owners.
Although most reputable companies will pay for postage on returns or offer a certain guarantee level, this small compensation doesn't help much when the company is staring at sacks of useless mail pieces. Consider the company selling a clothing line to pregnant women. A list of women who have purchased maternity clothes from another manufacturer or a list of women who subscribe to a magazine targeted specifically to pregnant women would be preferred over a list of women who are simply in their childbearing years. Consumers who have made frequent purchases and have purchased in the last one to two months make up a preferred list. One that is rented too often may be experiencing mail burn-out.