Microsoft apparently has purposely removed the drivers for Ethernet adapters from Windows RT, even though they seem to work. And they seem to actively block third party drivers for Ethernet too. It's an effort to kill Ethernet in favor of WLAN. Read the comments - some commenters posted links where manufacturers claim that they were asked by Microsoft to pull Ethernet-adapter drivers for RT!

The driver that enables certain USB Ethernet adapters like the Plugable USB2-E100 to work with new Windows RT devices like the Microsoft Surface has been pulled from the chipset manufacturer's site (ASIX). Microsoft is requesting that it be pulled from all downstream sites also.  Microsoft did not intend for this driver to be distributed.

Some have found hacks, but 8.1 RT seems to disable those.

Very disturbing. My theory why they are doing this, is because Ethernet gives too much control to the users: You can simply pull the cable if all the phone home gets too much. With Wi-Fi it's more difficult, - some devices don't even have a turn-off button for Wi-Fi connections anymore. Sure, you can turn off the Wi-Fi router, but then you disable all connections, for all people in the house (often these routers are a combined device - you turn off your TV and phone connections too)

Together with the forced online-accounts in the 8.1 beta and all the forced-online requirements in the original Xbox One design, it paints a very dreary picture. Microsoft wants to FORCE an ubiquitous and inescapable cloud. It's not a natural development anymore, but pure pushing, forcing and bullying on all fronts - removing drivers, killing off previous offerings (Office family pack) to push the cloud versions, and other measures. There is only the stick, and no carrot.

This guy might be an *, but Microsoft's actions validate his conclusion:

As time passes, more and more companies will find innovative ways of ruining the accepted, efficient workflows, just for the sake of money. You will find yourself clicking ten  times more buttons and options just to get what you could do so easily in the past, RE: Windows frigging 8.1 and friends. The normal menu is not coming back, ever, and you will see yet more forced online integration and similar crap cropping everywhere.      

Then, it will become subscription based *, with monthly fees and mandatory online checkins. Following the  trend, you will get mandatory ads in every program, and it will be against whatever law or license agreement to remove them. You will not be able to install programs that were not preapproved by this or that company. And so forth. This is your bright future, and it will happen slowly, so that people do not resist violently.

He's wrong with one point though: It doesn't happen slowly at all.