I would say, more likely that people were just free loading and not actually buying anything in DFO.
Had to go from airport to south east Melbourne yesterday, and honestly, taking
bus 901 to Broadmeadow, then train into city then continue down south only took 0 to 30 minutes longer than taking
Skybus Peninsula, as 901 had reasonable frequencies and trains don't get stuck in traffic, while Skybus is only hourly and could have stuck in traffic. If you just miss the hourly Skybus by 10 or 15 mins, you would spend 45 minutes sitting at the airport, may as well jump on the public bus 901.