Some time ago I was playing around with 10GbE using a Macbook Pro. At the time that meant a Thunderbolt adapter (and still does). Thing is, the one I got was essentially just a giant heatsink [1]. It was a beast and belied just how much of a problem heat distribution was. I'm not an EE so I'm not really sure why, other than by looking at what high bandwidth cables have done since.
10baseT (!0Mbps) came out in 1990 (there were non-twisted pair earlier versions). "Fast Ethernet" (100Mbps) came out in 1995. Copper 1GbE came out in 1999. Copper 10GbE came out in 2006. Ethernet seemed addicted to 10x'ing every version and 10GbE is really where everything fell apart. Or at least, it's where it got hard. We never really got mass market 10GbE. The controllers were too expensive. The cable requirements were quite high. And heat was an issue.
1GbE really was fast enough and 10GbE was a massive jump that I even remember thinking at the time that there should've been intermediate steps, which is what happened in 2016 with 2.5GbE and 5GbE.
Now compare to Thunderbolt, introduced in 2011, which has completely surpassed Ethernet bandwidth, in part by putting chips in the cables, but of course the big difference is cable length. A copper cat 6/7 cable can get to ~100 meters, which is also why the power is so high: attenuation.
but I guess my point is that 10GbE over copper was a mistake. We'd reached the point where you really had to swap over to fiber.
[1]: https://www.ebay.com/itm/127178476193