Earlier quoted context omitted.
You say this, as every major platform migrates towards apps. Windows 8: (huge push on becoming) app centric. Mac OS X: (becoming )app centric. Android: app centric. iOS: app centric. What OS isn't? Linux. (eh, edit, this really isn't fair. Linux is as "app-centric" as I need it, though the "linux is so secure" assumption is uh, going to become fallable as its competitors approach an app-centric, isolated model. (also…
> You say this, as every major platform migrates towards apps. That's the way it goes with these damn computers. In circles. I recommend you unpack a bag of floppies, get yourself some Windows 3.1 and take a good look at Program Manager.
It goes in circles because computer technologies are bursty. With Win95, managing by window was reasonable because having >10 windows would usually crash the box. That's also why every window was a taskbar entry, as there was actually room for all of them... By WinXP, when virtual memory became more robust and RAM cheaper, you needed to sometimes collapse taskbar buttons by app to make them fit... And now in Win7, it's the default with just big icons. People leave way too many windows open now because closing them is a chore, and people are crappy/lazy memory budgeters. Apple realized this with iOS, and ported some relevant concepts back to Lion--apps should be able to close and restore at any time, and their open-ness is irrelevant to the user. So yeah, that's why we're back to thinking about apps; windows may be what you most often interact with, but they are no longer the mental unit of desktop management. It's now all about task-->app-->windows.
As an aside, let's consider how effed up MDI is, the inconsistencies in window/toolbar management between Win Office apps, and how the Mac "one window per document, palettes appear on app activation" scheme has managed to stay remarkably consistent for over a decade.