Tannin said:
Shuttle: no good supplier at present, Blake.
Coug
And the point of the additional 4 pins 12V connector is to provide additional current to the motherboard and probably also to give a better current distribution on the mainboard, since there's more than one source for the 12V supply. That's more or less the same reason why there is more than just a single Vcc pin on a CPU pinout.
In short, it's an increased insurance for proper current supply to the mainboard. You can live without...much like you can live without a backup for your hard drive.