If you take a look at a modern PC motherboard, you'll see there's already a considerable amount of board space allocated to local voltage regulation: modern CPU

If you take a look at a modern PC motherboard, you'll see there's already a considerable amount of board space allocated to local voltage regulation: modern CPUs can require multiple different voltages none of which will be supplied by an ATX power supply. Often it will be desirable to have fine control in software over the regulated voltages to maximize system performance or stability. RAM and other devices on the board, as well as high-powered devices like GPUs probably need their own voltages too. From my perspective, it's just the continuation of the trend to its logical conclusion: if you're going to be generating eight different voltages on the motherboard, GPU etc. why not just add an extra two?