Why would an airline charge less for a longer flight that passes through the destination city than for a shorter flight to the destination city?

Some travelers use cheap travel websites and book at off-peak times to save money. Other travelers have tried to increase their savings by booking a one-way ticket through a connecting city where they intend to stay in the layover city. For example, a traveler flying from Los Angeles to New York City may find it is less expensive to book a one-stop flight to Providence that connects through New York City and then not take the last leg to Providence. This practice, known as using a hidden city fare or skiplagging, can save the consumer money on the trip. However, it prevents the airline from selling the empty seat.