Due to a few reasons.
The economy is a bit slow, not much money around. Each time that happens aircraft fly less both for work and more so for play aircraft.
The transition in regs is also playing a big part.
The quality of appy's has been declining (odd good one around) but wages in new award increased a lot, an extra 2 weeks of TAFE added. Don't quote me but from memory it was around $700 a week for a 1st year. They will always break or do something that costs lots (connect battery wrong as both lugs are red crimps $6k plus 9 years ago). You can claim that but pay out your premium and brace for the next years insurance bill. There are 4 weeks leave, 12+ melb cup and other local events days in public holidays, 10 sick days and 9 weeks TAFE. This all works out to about 1/3 of a year not working but paid while knowing nothing and requiring supervision. A appy normally becomes useful in the 4th year and normal move on after that. So we stopped taking on appy's a few years back.
When the AUD (Ozzie $) was strong + $1 to USD (USD was actually weak too) the States increased their prices in things inc Aircraft parts, now prices that exchange rates have normalized some what - we are paying about 40% more than we did when exchange rate was before about 73 cent to the $1. That is far greater than CPI over those years and putting pressure on our industry both AOC's and COA's.
Then things like SID's and Live export bans have effects, I have log books of aircraft I have not seen for 5 years but I am sure the windmills have seen them.
Mining also plays a big part in aviation from FIFO to many hours of survey. I have done many 100 hly on survey both here in Oz and in Africa, normally every 2 weeks you see that aircraft both singles and twins. No need to tell you how the mining industry currently is.
And after 35 years in the game I am just getting old and need a change.