Lightning is an Apple propriety connection - and no doubt Apple charge a license fee under MFI - which hikes up the manufacturing price - even considering IF Apple will allow a license for Oculus Go - which doesn't even attach to any Apple devices. Not an option.
What benefits of using usb-c is there, over micro-usb for this device? Very little. Its just used for charging.
I added Lightning because for better or worse need to deal with Apple proprietary if you're using Apple devices, but it is at least a robust, compact, double-sided connector.
Micro-USB is extremely flimsy and single-sided. If you're not using something proprietary there's no excuse to stick with it. The ultimate benefit if you choose USB-C devices is that as time goes by, you start to not need to carry micro-USB cables around, and suddenly the cable that charges your computer also charges your camera and also charges your phone (Android) and your videogame console etc. Yes, this was the case with micro-USB as well except for computers, and it was "ok" while it lasted (again, not a good connector) but the higher USB-C capabilities promise to supercharge this reality, which will only happen when (and not if) manufacturers start to update their USB standards.
I don't buy micro-USB devices anymore, unless I have no other option, like, say, in console controllers. And then I assign to them a dedicated cable like they were proprietary. It's a sad state of affairs, but it will get better.
Any micro-USB device released now is just pure friction, because the same manufacturer will have switched to USB-C in 5/10 years tops. Maybe they are holding it out as a further bullet point for future iterations, maybe they are saving pennies on the dollar, maybe they are just slow to adapt, but neither case paints a good picture for the company.
$200 may seem little for a standalone VR headset, but it's too much for me to spend on a micro-USB charged device. I'll wait for a faster version 2 or 3 with USB-C, if I'm still interested by then and if the product didn't flop.