As for carrying a knife it is pretty much illegal to do so, no reason you can give a cop will be legitimate and I have seen this to be true in my experience here....
This can depend on your occupation, for example Paramedics are allowed to carry pocket knives, if they wish so, e.g. in the case of a hanging, cutting the rope quickly is important, as there may be a chance to save them...
Electricians are allowed pocket knives, to help them strip wire if they want to use a knife to do that, or cut tubing or other stuff that they may need to cut. But they are meant to leave it at their 'office', which is hard as if they are contracted out to a site, well they can't exactly leave it there until the next day of work.
I also know that you can carry one whilst camping or hiking, but you have to be in the area you are camping/hiking at. You can't carry one on your persons whilst driving to the campsite. Meant to be in your pack.
Also as you said you are leaving, I guess you won't have to worry about silly Oz knife laws, who knows it may change?
Can I also ask, you said you used to do security, did you try to carry a knife then - I can see why weapon laws would not allow you to carry a knife, becuase by their reasoning, you are not using it to perform a job, even though security was your job, I'm not sure you would be using it to cut an apple up?
Plus I guess there is the chance that someone who is angry at you, comes back with some mates, and your knife gets used against you.
But otherwise I totally agree with you, I still carry a small spydie dragonfly, even though I may not have a legal reason to do so, however SD with it is at the back of my mind, as even if it saved my life, in a court trial, it would be pretty messy I'd imagine.