Without all the finer details points as to why flying has dropped off there's really only one reason at the end of the day us working plebs understand/know, COST, pure & simple.
Flying privately or even for business purposes is a huge expense & when Co's are always trying to find ways to reduce overheads & increase profits or at least stay afloat what gets the chop real quick? The luxuries or convenient items such as Co funded getaways & the Co Limo, the flying machine (if that be the case).
Private flying comes under the banner of that ever decreasing 'disposable income', something Aussies once had a reasonable amount of once upon a time. I'd hate to imagine how much an Hr it would cost to hire a 4 seater for pleasure.
Wmk2