Bicycles stand out too much in Australia. If it's unique and cool, people will fuck with it. Furthermore, it's far easier to physically pick up a bike and chuck it in the back of a van than a car, and not very many people are going to interrupt a thief using bolt cutters, particularly if they're wearing hi-vis.

So you're left with needing angle grinder resistant locks, with none of the portable ones being long enough to fasten around the body and any fixed stand so you have to get creative about where you park, and even then somebody might just unbolt the fixed point. Creative means it might be away from other bikes and or cameras, reducing security.

Then there's no clearly visible registration so even if you report a lost bike, nobody will easily be able to tell if the one being ridden by is yours or someone else's...

Eliminate theft and you're still left with vandals, and there are a LOT of destructive people with plenty of time on their hands...