It's designed to be a wireless router without a lot of extra fluff. If more lan ports are needed, add a switch behind it (though it'd probably be better to have the switch elsewhere unless it's a really simple network). The USB looks like it's used for admin tasks like updating firmware, so I don't see why they'd need to add more than USB2.0.
USB 3.1 brings this new connector, usb-c. Many newer devices use that connector these days and customers may wish for a port with that connector. If you have a laptop with such a port, you'd be able to use a usb-c to usb-c cable to connect it to the router, perhaps for debugging, without needing a usb-c to Ethernet dongle, plus Ethernet cable. Plus not needing to disconnect the single LAN port.
USB-C Serial console != USB 3.1 port. Nor does a usb-c power supply port count either.
No need to get defensive, I wasn't the one asking if there was a use for USB > 2.0. If you didn't know before, now you know. If you did already then at most you read a sentence full of information you already knew. Hardly a terrible offense. Other readers who might not have known also now know. :)
I wasn't asking if there was a use for USB 3.1, I am already aware of how it's commonly used on routers (apart from the LTE fallback the other commenter mentioned. That's pretty cool). But even so, your comment didn't list a use for it. You listed uses for usb-c, most of which it seems that it's already capable of. It's not a big deal really, just clarifying.
