Australia is FAR more litigous than UnZud.
Any event organiser needs good insurance cover for two reasons:
1. To cover their arse(s);
2. To be gain permission to run the event.
Basically, the way its evolved is that someone gets hurt and then chases who-ever has the most cash. So if the host club is poor, they go after the Clerk of Course personally, or the land-owner, another rider or whoever else they think is the softest, juciest target. Even if they are unsuccessful in their claim, the stress and cost is enough that NOBODY will be willing to stick their head into the noose ever again.
So instead, we pay a truckload in insurance to be a big, soft, juicy target for the ambulance chaser lawyers.
There was a case in Orange, NSW about 15 years ago where a guy crashed and died in his Mini at an organised event. After some years, his widow began looking for cash. After the organising club simply disolved in response to the threat of legal action, the widow and her ambulance chaser ended up trying to sue the then-retired local police commander who had given the event the OK. Needless to say, the new commander was not the slightest bit interested in approving any vaguely-similar events within his command area, and virtually everything stopped for a couple of years until he could be convinced that CAMS/AMSAG insurance was going to be a bigger, softer target than himself...
In most Aussie states, disclaimers mean sod-all. The law changed in NSW about a decade ago so NSW disclaimers mean something - if you sign a disclaimer in NSW that says 'I recognise and understand the risks', it takes away a whole lot of the paths to claim that your crash was someone else's fault. This makes the whole process of suing someone for negligence much more difficult/much more likely to fail, but (ironically) it still hasn't been tested properly - it needs someone to put up the cash and fail before everyone puts their faith in the power of the disclaimer...
Also, good intentions to not sue mean nothing when you've got many thousands of dollars worth of bills to pay and no way of paying them (insert a rant about the NDIS here). Similarly, you might recognise that your crash was your own fault, but your widow (or widower) probably won't have that same perspective.