Some agencies don't want to obligate the funds until they're sure the trip is going to happen. It's EXTREMELY ANNOYING for those of us who work for agencies that require us to ticket the official itinerary and then change it (vs. ticketing the way we want and paying the difference out of pocket) to take a personal trip "on the side" with an official trip. Luckily the new GovTrip system that we use defaults to ticketing 3 days before but can be told to ticket immediately once the travel is authorized.

It's especially strange when you consider that the contract fares, capacity-controlled or not, are always fully refundable. The only thing lost by ticketing immediately is the ability to do something else with the money in the meantime if the trip is cancelled. The whole process is a little odd; I once had to reimburse the government $80 because I changed a UA flight to a different flight on the same day, which shouldn't have changed the fare. Somehow the travel agency had collected YQ on a fare that didn't have one, so .bomb refunded it when I touched the reservation.