Because sooner or later businesses *have* to pay training costs. It's unavoidable. Windows 8 (even Windows 9) will be on the market for quite some time before the majority of businesses upgrade, many people will learn on their own how to use the OS, mitigating some of the costs.
What strikes me as laughable (though the point for once is valid) is that training costs in businesses and enterprises are a BIG reason not to change out an operating system - the reason why it strikes me as laughable NOW is that originally heard it coming from businesses running NT4WS that didn't want to upgrade to Windows 2000 Professional.
Fellow Neowinians, I was in an enterprise (specifically, a broadband-support call center for Big Cable Company) that DID such a changeover; the changeover was the entirety of the eastern US' operations. Every single desktop. (The servers were involved as well - they would upgrade to Windows 2000 Server once all the desktops got upgraded.) Despite the alarums from the IT types, the biggest issues were, in fact, applications - not training. Why? We, as users, pretty much helped each other through the rough patches (the biggest *rough patch* for users was printing - however, once users figured out how to use print-queue browsing to select un-backlogged network printers, it actually got EASIER than NT4WS did). Why would users not help each other through a 7->8 upgrade? Are you implying that users are, in fact, MORE selfish today?
For the average user, the difference is that the Start menu is missing - period. In terms of how to maneuver around the OS, there is NO other difference. How many users - even those still using Windows 7 - center all their operations around the Start menu? Now, if you are a user that does, in fact, center most of how you get to things around the Start menu, its excision is going to be massive. (That is something that I have pointed out going back to the Developer Preview.)
However, other than that, nothing really changed from a user-operations POV between 7 and 8. The Superbar is still there. Taskbar pinning is still there. (In fact, both have gained additional teeth due to applications that launch on startup now appearing on the Taskbar, in addition to the TaskTray - this was not in Windows 7.)
What I am seeing is those that miss the Start menu deliberately calling attention to it - in hopes of staving off a final demise when support for Windows 7 goes away in 202x.