CTP and road maintenance fees goes onto your licence. CTP is calculated on YOUR risk, rather than arbitrary, discriminatory nonsense.
The more you think about it, the more it makes sense.
The reason it won't happen is that us multiple vehicle owners are subsidising the single vehicle owners - the majority of the population would end up paying more, especially the single vehicle families.
(Currently five registered cars and three rego'd bikes between two licences at my house...).