Comment by tardedmeme

Even though both USB and Ethernet transport bits, the surrounding ecosystem is so different that it couldn't really be a replacement.

Devices plugged into an Ethernet network are true peers, but USB is master-slave by necessity. Ethernet devices have unique addresses, but USB devices can be anonymous, only identified based on the port they're plugged into. Ethernet is best-effort with buffering and packet dropping, but USB provides guaranteed delivery with tightly bounded latency. Ethernet signals must travel up to 100 meters but USB requires the host and device to be within a few meters. You could reuse the physical wires, maybe (we already do! USB runs on twisted-pair) but nothing else, from the connector to the topology, is usable.