You may not realize it since you are in Australia, but practically every manufacturer does exactly that, including Blackberry, HTC, LG. They all make multiple versions. I still don't think Verizon will sell it.
And what you, and the rest of the USA doesn't realize, is that the other networks in the world build their network out to suit the phone, not force the phone manufacturers to build the phone exclusively for their network. The latter is what has been happening in the US for the past 15 years; The providers build their network, try to pass that off as the standard, and tell the phone manufacturers to build the phone for their network (read: locked).
2000, one provider in particular, Sprint, told one manufacturer (Nokia) that they will make a phone for their network, or they will never sell them. So Nokia gave them the big F.U., and stopped making phones for them, as everywhere else (Except Verizon), TDMA/GSM was the standard network protocol (NOT CDMA) being used worldwide. There were a lot of things that my friends could do on their GSM network that I couldn't do on Sprint's network at the time, despite the fact that we had the same model of phone. The difference: the network.
So what you're saying is from a US-centric point of view, when everywhere else in the world, this is wrong.
BL.