To build of Kirkswans post, Sydney has a myriad of competing sports. Most AFL supporters I meet are from other states. Worked with rugby fans, and cricket enthusiasts, but struggle to find NSW born AFL fans. So much competition when it comes to sport.
My experience has been different. I find that the NSW born footy supporter numbers are getting bigger and bigger.So in short... all the codes there are stealing fans from each other?
I have been associated with Sydney footy on and off for 40 years now, and the supporter and participation numbers are massive compared to 1981.
Back then it was referred to (with a sneer) as "aerial ping pong" with ultra tight shorts. Now it is part of the Sydney landscape.
An example is a work colleague. She and her husband were dyed in the wool Parramatta Rugby League supporters, season tickets, you name it. The Giants came to their son's school and he became a Giants supporter, did Auskick and now plays local footy. They go to Giants games with him. Meanwhile my work colleague became a Swans supporter, as did their daughter. (The husband refuses to budge. Fair enough.)
A lot of my Rugby League mates have gone from distain to support, albeit secondary to their Rugby League.
I read a few years ago that NSW Auskick participation numbers were higher than Victoria's.
Junior girl's footy has increased exponentially.
When I started Sydney Uni had two sides, and in 1981 started a third team in the U19s. Sydney Uni now has 8 men's and two women's teams, and that is reflected across all the clubs.
Phil Gould is a multiple premiership winning Rugby League coach and media person. When he took over as General Manager of the Penrith Panthers Club, he used his media profile to raise deep concerns about junior Rugby League participation numbers in the area - because the kids were playing footy, due to the Giants being at every school. The Rugby League see footy as an existential threat.
So yes, there is an element of codes stealing fans, but fans are being, and have been, created generationally.