Well this is opinionated but I think it has to do with blame laws.
At the moment if you crash your vehicle its considered to always be the driver at fault.. but what if the driver isnt well, driving. It could be blamed on Tesla which isn't exactly great for the company. Some states have changed this (Victoria is one I know of) and we should be getting Australia wide shortly.
You can read more about 'automated vehicle' laws here this is from Victoria though.
Parliament of Victoria - Automated Vehicles
Australia wide laws are either already here or coming soon, apparently by around 2020. But thats in political time so its 3020.
Automated Vehicles in Australia
Preparing for Automated Vehicles
Atleast they are laying down the groundwork for automated vehicles and are actually taking them seriously, I was pretty worried they would have just locked down everything but they havent
In Victoria it seems pretty damn good, I think its just road design and maps then. But lets also consider the fact they we are a pretty niche market too, we have zero incentives for EV's infact a disincentive with our luxury car tax. Its not exactly a priority in Australia at the moment.
I'm not saying that its regulations entirely but its definitely playing a part.