Hold on.. lets not use that broad a brush.. Its not just cats that have declined.. I recall mirror trainers having A,B,C & D division racing on a Saturday!! With fleets of 30+ in each division.. Try and find a fleet of 6 and your pushing it today!!..
Clubs that are only cats? Did you count the Cat club at woodman point Western Australia? It hosted a world T title back in the 90s.. However Nedlands YC, Shelly YC, Maylands YC, Whitfords, mullaloo YC, And most regional YCs in WA have at least one cat racing to my knowledge.. Including the Cruising YC at Rockingham!!
The big IRC clubs have only cruising cats and tris no racing.. These are however the bulk of the cash in racing in WA... They are the ones with the royal warrants.. Have the cash from pen fees.. 500 pens at $3000+ a year soon adds up.. Then add the bar contribution which is set as well..
As for the Sydney scene.. I recall in the 70s sailing at a club on sydney harbour.. 3000 members 300 involved or related to sailing (dad/mum/uncle of a junior sailor counts!).. Rest involved in the drinks and pokies.. So nothing has changed..
Today kids have other unfortunately "sicker" distractions..
BTW Nedlands YC is still IMHO one of the great sailing venues.. It has enough grassed area to rig a world T championship and a world A title at the same time.... Would be brilliant for a F16 Title!!