Definitely minimizing wasted empty seats. Additionally, by encouraging people to book far enough ahead, they can change equipment to match the demand or add ano

Definitely minimizing wasted empty seats. Additionally, by encouraging people to book far enough ahead, they can change equipment to match the demand or add another flight to that day. It also allows them to price discriminate against business travelers who tend to have deeper pockets (flights expensed to their company) and tend to make lots of last minute travel changes (need another day to close a deal, etc). Losing the ability to ramp up the price on these types of travelers would mean higher fares for everyone and likely fewer ticket sales.