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.
It is still a major non-trivial difference between implementing USB-A header (super trivial, just wire up the lines) and implementing USB-C - needs additional TCPC with enough ports, located nearby enough, plus flash rom, plus possibly an extra interfacing chip per each port. And that's if you only want reasonable USB-C that does just USB with maybe a bit of Power Delivery (but not too much). And then you need to ensure firmware handles it right (and that's not including bugs like Intel "firmware quality" leading to broken flash roms on entire product lines with thunderbolt controllers).
There's a reason why USB-C ports on laptops are often very... "clustered", let's say. Makes it reasonably easy to route signals if you're routing just what's essentially USB+DP or USB4, and I2C, and put 2 port capable TCPC and necessary switching and support circuitry near the port.
