Many aircraft require the charterer to pay a daily minimum in flight charges in order to reserve.
For short trips, it is often more costly for an owner to fly the airplane, pay a crew, devote operational resources to booking/payment/client service/etc. than it is to charge less than 2hrs of flight time to a customer.
In order to protect the owner from losses on such trips, Daily Min fees are imposed. Daily Mins typically range from 1.5 – 2.5 hours, depending on the aircraft.