Don't forget the gas stations too.

For this generation 4x 8pin might not be a big deal, but in the future you could be looking at 6x 8pin or more. Also there are additional benefits when the 12+4pin is paired with an ATX 3.0 PSU.

You have to remember that with an 8 pin connector it's really just 6 pins for the power delivery.

They could have done something like they did with the dual 8 pin cables, basically made a pigtail 12 pin with each connector at the GPU just doing 300w for 600w total, but you'd still have 600w from the single 12 pin at the PSU, plus they were trying to reduce the number/size of connections on the GPU.

Only 6 pins in an 8 (or 6+2) plug carry power. Also those 8 (or 6+2) pin cables came in the daisy chain/pigtail variety, meaning each cable had two GPU plugs each capable of doing 150W so 300W total for 6 wires from the PSU.

We now have a single plug cable (with no pigtail/daisy chain) that has 12 current carrying wires and supports 600W, it's no different than before, it's still 50W per wire from the PSU (or more specifically 100W per pair).

Think of the new 12 pin connector like two dual pigtails 8 pin cables from before, they just moved the sense wires to the additional 4 and consolidated the plug, the number of wires from the PSU that carry current hadn't changed.

They've effectively halved the number of connections because they've removed the ability to have a pigtail/daisy chained connector and separated the sense wires.