I work some in PC sales and repair, and this is actually true. Probably 95% of our consumer customers use their PCs for no more than a Chromebook will do. Of course, a few will do more and business users as well, but the average user does email, Facebook, and browsing. That's pretty much it!
I agree, but even if users do more, the Chromebook is still a viable option. I still know a lot of people that desperately want MS Office on their laptops, but that is just because they haven't yet grasped that you can go to Office Online or Google Docs and get a subset of that functionality for free. The online versions are rather simplistic, but the truth is that the average Office user hasn't advanced farther than what MS Office was capable of doing fifteen years ago. For the occasional letter or quick & dirty spread sheet, the online versions work fine.
Then we have browser games, which are becoming ever more popular. Netflix is provided through the browser, as is YouTube, and most of the other services people use. My Girlfriend works in the finance industry. She is around office computers all day, but when she is at home, she could easily get by with only a browser.
What difference is that from a Linux netbook? All that has is a browser with not much else. You say "all of the programs were on Windows" as if they're taking on the iPad, which is not what this move is about.
Again, my point is not that Chromebooks can easily entice consumers away from Windows. My point is that Windows doesn't have the same ability to retain users as it once did. Today, many people can easily imagine a home computing environment entirely without MS or Windows. This is definitely different! Not because Chromebooks are so much better. They aren't. It's just that Chromebooks are reaching that level where they are "good enough", and most consumers don't care about anything that goes beyond "good enough".
Yes, Chromebooks are just modern Linux netbooks. The difference that you fail to see is that five years ago, an internet browser wasn't half as capable as an internet browser is today. Today, for a lot of people, an internet browser can even replace MS office. The internet browser is slowly becoming what the OS used to be... it's the foundation on which everything else runs. Google is the main force behind this transformation, and it will continue.