Even with the best intentions, there seem to be valid operational reasons for airlines ignoring them
Its called 'Schedule'.
I often hear people saying ATS stands fo ATService, which is true. We (airline/charter) are also providing a service. A service to our customers, the passangers. If our 'schedule' states we will have them returning to Perth to their homes, loved ones, connecting flights or what ever the case may be, then it is reasonable for them to assume (and make arrangements) based on that scheduled arrival time. That is OUR service. And it is OUR reputation that gets stained. I cant tell you how many times (and its getting more frequent) that I hear pax complaining that "your airlines crap. You never run on time", all because we delay on the ground to wait for our PTL time. We make appologetic PAs, and you can rest assure that I blame it fairly and squarly on WAC and not ATC, but the punters aren't interested in excuses.
Our average ground delay yesterday was 34 mins (and that was after a 30 min taxi delay to depart Perth), but often our ground delay is 1 hour. A 1 hour ground delay for a 1.5 hr to 2 hour flight. Thats just plain rubbish. The system (although not the fault of ATC front liners) promotes in my opinion PTL breakers, and I dont blame them one little bit either.