This isn't inherently true - the fare rules typically dictate that the passenger must take the next available flight or any flight within 4 hours, meaning that if there are multiple flights within 4 hours, they can take the one 3 hours later rather than 15. However, if there are only 2 or 3 flights a day to their next airport, they aren't able to book a flight with a +4 hour connection if there's one within the bank (eg <1 hour) without splitting the fare into two parts (eg buying a one way outstation to hub and hub to another outstation).