I can think of a few reasons.
1. The VE production run went far too long without substantial changes being made to the car's appearance. IMO, the VE was started to look very dated. It had lost its market appeal and people were looking to more modern designs from other makes. I realise the GFC and various other financial factors meant the production run was much longer than originally planned, but the Series 2 facelift could have been much more extensive, particularly internally.
2. As you point out, the VF is a huge improvement on the VE's interior. Holden recognised that the VE looked cheap and nasty inside and I read somewhere that the only carry over part from the VE interior is the console armrest pad. Everything else is new and far more up-market.
3. Perhaps a bit of patriotism has crept back too. The VF looks desirable and people know that once it's gone, it's gone.