This is an opinion query, so no flames please, just your ideas. Why wasn't Ethernet adopted as the defacto communications standard for all peripheral devices?
O.k. I guess there is the adjunct circuit power supply that you get from USB, but frankly I think I would have been happier without that, and with one just super fast standard.
Ethernet IEEE 802.3 is THE standard
and so is wireless IEEE 802.11 a/b/g/n
and for some really simple communications a basic serial connection is all that is required: Tx Rx Gnd Keep It Simple, Stupid
Everything else with names like 4g 3g usb3 usb firewire esata parallel vga pata adb thunderbolt localtalk pcmcia hdmi bluetooth infrared cellular scsi ... is just silly, but profitable for the corporations sustaining the industry of cables, connectors, adaptors, and new fan-dongled specifications that do no more than the previous version did, except that now you are sold that you need the new one.