This is the maximum amount specified by the PCI Express standard for a x16 slot (PCIe 4.0 and 5.0 spec). If a graphics card requires more power, it will typically have additional power connectors ...

PCI Express (PCIe) has been around since 2003 ... there was no need for a specialized graphics card slot, using e.g. an x16 PCIe slot with 16 lanes. It does however mean we’re using serial ...