From the article Clark linked, obvious there are valid counter arguments (like azimuth with the anti-ice fluid covering the window). But he makes some good points about how we did it at the dawn of the jet aviation with slide rules for the first time ever.
"I have yet to have a boom operator give me a justification for this new virtual boom operators system. If aircraft contractors say it will cost way too much to physically attach a boomers station to a 767 then the USAF should ask them how they did it with ease at the dawn of the jet age with the KC-135, and then again with the KC-747 in the 1970s, and then again with the KC-10 Extender in the early 1980s? What magic wand did Boeing and McDonnell Douglas have back then and where on earth did that magic wand go because we really need to find it. It seems as if with the loss of that wand, our drive for simplified, low-risk procurement solutions based on proven systems and successful practices was lost as well.
Also, consider that Boeing will elaborately modify their commercial aircraft for military needs. Huge radomes, massive antenna fairings, weapons bays and just about any other modification you can imagine have been done to Boeing airliners over the years. So grafting a rear window onto the a 767s tail seems like a small request in comparison.
Why change a proven, robust, and known system that has safely worked for over half a century? 3D goggles can break, stereoscopic cameras can go dark and control consoles can malfunction, but a window is always on.
I am sure Boeing and Airbus have some big cost analysis describing how somehow such a system will save the USAF money over decades of service, but really, that is very hard to believe as it requires new training simulators, lots of high-end hardware to install and maintain, and most importantly, development time and money. In actuality, those reasons may be exactly why this new aerial refueling interface exists in the first place, because it will it will mean big development, support and upgrade dollars for defense contractors for decades to come, something a mechanical boom, some levers and window cant provide."