You have three options: 10 GbE, 1 GbE, or 0 GbE as dongles or no dongle. If they included ethernet then they would be taking away an option. Dongles are annoying. But if you have a big dongle that is the eGPU, then what's another?
Simple answer.
Fully equiped eGPU enclosure would act like a dock in home = more GPU power, external screen, corded mouse and kb (if you wish these), ethernet and everything what you want to use at desk connected to this enclosure and by single cable to your MacBook.
Going out of home?
Unplug one cable and you're good to go.
Looks like it's too much to expect...