The netbook of 6 years ago had an ethernet port and ran Linux out of the box. Feature parity has not been achieved by later models, if this is reimagining things they're imagining with a case of Alzheimer's.
Consider the following tuples: (Apple, loved by all) (Apple, no Ethernet port) (Microsoft, not loved by many) (Microsoft, Ethernet port). Correlation is causation, right?
Rather than requiring movable parts, it could be built into the keyboard with some sort of protective cover on both top and bottom (if there's enough clearance on the bottom for the end of the ethernet connector).
It's possible. It might be too costly to get acceptable reliability, but it's possible and it's been done.
Note: I'm using an 802.11ac router and a laptop with a Centrino 6300 chipset. I have the 5Ghz spectrum all to myself. For bulk transfers I get consistent speeds of close to 100Mbit.
For daily stuff, sure. When I need to shift gigs and gigs of media or VMs or whatever though: Cabled is the only way.
It's the only thing which is reliable enough to not make me tear my hair out and for stuff like this performance really matters. Especially when it's orders of magnitude faster. To some people, not having a physical ethernet port seriously is a deal-killer. Yes.
Apple has successfully shipped models without it, but Apple's biggest market-segment isn't IT professionals. It's non-technical people fed up with Windows and hipster bloggers.
I use an old macbook (that has an ethernet port). When it comes time to replace it I'll buy a dongle with the new one, and on the relatively rare cases I actually need it use that. I can't really imagine it ever being a significant issue to me.