Unfortunately, it usually does take a tragedy for something to be changed.
It should be noted, however, that NSW does not have any speed restrictions past emergency vehicles. SA was the first state to bring it in and I don't believe any other state has legislated it (I could be wrong there).
Even though it may not be as slow as it should be and definitely not adhered to very well on roads like freeways and highways, at least we have some measure of protection in place, unlike the other states...