I mean.. my X670E motherboard (a high end, modern mobo!) has only ONE usb-c port.. it has, in comparison, 3 usb-a 10gbps ports and another 4x usb-a 5gbps ports. Given the headset's main use case to be plugged in is for PC-VR game streaming, it makes sense that they'd go with USB-A. Maybe in a few years they can switch but right now most desktop mobos barely even have usb-c.

Some motherboard have a rear USB-C, but no internal front panel header.

Desktop is so far behind on ports.