I don't think that Microsoft had any foresight into the 2006 Intel transition in 2004. Office 2004 was on the shelves for 18 months before and ~24 months after the Intel transition when it was replaced with Office 2008.
And that's 24 months that they had to do something about it. They COULD'VE come out with an update that permits native Intel support for 2004 instead of requiring an upgrade to Office 2008. But they didn't. They could've done done a back port even up to now. But they haven't. And for obvious reasons: they'd rather you buy the new software.
So why does Microsoft get a pass on this and Apple doesn't?
It's 7 year old software. That's a good run! But it had to end someday. It's time to move on.