If a collector has done their job correctly they should be able to to finish a phone call with a debtor, and both will feel good about the call. The debtor can feel good, because they will have fulfilled their obligation to pay a debt. The collector will have done their job.
By collecting past due debt, the collection industry can help keep the cost of goods and services across the nation closer to their real costs. Without having to build in uncollected debt into their cost of goods sold, companies can pass that savings on to all their customers.