However, HDMI (which is primarily four pairs of high speed serial--just like Ethernet) and later Displayport became the "solution" because of all the people pushing HDCP.
Thunderbolt was the "solution" to the fact that USB 3.0 wasn't coming down the pipe fast enough. And that drivers were just too complicated. Why solve the simple problem of loading a driver at boot time when you can just give the peripheral complete control over a system bus? What could possibly go wrong?
USB 3.0 is an "evolution" over 2.0 in the way that a jackalope is an evolution--splicing two completely unrelated things together (USB 2.0 spliced with 4 high speed pairs--just like Ethernet). But you can't charge a licensing fee for Ethernet ...
(And yes, I'm assuming bare ethernet frames, not IP or such)
However, Ethernet IS cheaper than USB 3.0. And Ethernet is significantly less complex. Look at carnage from all the audio interface people trying to come to grips with Thunderbolt and USB 3.0. Whereas, people implement gigabit Ethernet interfaces all the time.
And this dovetails with USB 2.0. In terms of complexity, I have found that Ethernet wins. I have started removing USB 2.0 from anything I can and replacing it with Ethernet when possible. USB 2.0 is such a pain to handle in terms of drivers while Ethernet "just works".
(Yes, sarcasm. Two can play.)
ethernet is a wire protocol upon which a TCP/IP stack runs on top of. if USB looked a lot more like ethernet, it would be far easier to write drivers for devices.
> it would be far easier to write drivers for devices
I can only assume this comes from a place of "I know a bit about ethernet and would like to transfer that knowledge to the embedded space." It certainly doesn't come from a place of "I write drivers for the USB and PCIe stacks and think ethernet would make my job easier."
There's also the matter of what HW/FW likes, which probably has greater bearing on the situation than what SW likes, and I can assure you that they'd be even less enthusiastic about the replacement than I am. Proof: they've got a choice! If they wanted to use ethernet, they could just do it. They don't. For good reason.
(Yes, sarcasm. That protocol is called Ethernet. And basically every high-speed interface we currently have is a bad reimplementation of it for political reasons.)