[wtallis]

You can get 40+ Gb/s over USB-C or connections like DisplayPort and HDMI by using thick expensive cables that top out around 10ft of length. Beyond that, price starts shooting up as you get either optical transceivers or active retimers/redrivers built into the cable assembly.

Ethernet over copper is designed for cable runs of over 300ft and has to be much more forgiving of poor quality cables and connectors. That means for the same level of complexity and power consumption in the transceivers, you're just not going to be able to get as much bandwidth.

Ethernet equipment suitable for 2.5Gb/s and 5Gb/s in consumer equipment (cheap, low power) is now readily available, but there's not enough demand to drive pricing down to parity with 1GbE and completely supplant it. 1GbE is good enough for most consumer use cases, especially given the dearth of multi-Gig WAN connections in the consumer market, the lack of popular use cases that would benefit from slightly faster LAN connections, and the continuing improvements to WiFi.