That's because Word, Excel and PowerPoint 2007 now all use different file formats: .docx instead of .doc, .xlsx instead of .xls and .pptx xlsx in lieu of .ppt.
Because Word 2007 saves documents in .docx, efforts to open a .docx in Word for Mac 2004 will generate ugliness that will look something like this:
My own take: Microsoft is taking care of its own.
I am a Windows user. It is more intuitive an experience for me. So that's where I come down.
If you are a Mac cultist (sorry, Mac aficionado) and you really, really want access to Office 2007 tools, well, I'm sure you know where your CompUSA, Fry's Office Depot, OfficeMax, Staples, etc. is.
That's what I think. But maybe you disagree.