@Thinkpad Fan - I'm not telling you how to use it, simply pointing out most common usages.
As for losing your Ethernet adapter, how about just buy spares? I keep one in my laptop bag and have some in the house. So I would never lose it if I need it because I don't take it out.
As for the travel router, I've used it to debug another router, it worked fine. Most travel routers have multiple configurations, so I can imagine people having issues, especially if the manufacturer poorly configures the default. But once its configured, its pretty much plug and play.
As for your suggestion of using thunderbolt dock. Here is the difference, again, when you are using Ethernet, you are tethered to something via Ethernet. But the same doesn't apply to USB. And USB is more versatile too. For the size of an ethernet port, you can fit 2 USB-C connectors. And 999/1000 would pick the USB. I am sorry if you are the 1/1000. But you can't blame manufacturers for making decisions which would bring in the most sales.