M.S. is obligated if they want people to do a upgrade, other wise, they will see less people would spend money toward their newer OS.
Specaially if UI is new they better bend over and make sure no Cx is being left behind.
That's why their Win 7 sell is so slugish. Vista sell was just a Joke. XP is still strong. Even though no NEW Computer can be bought with that OS.
I had a feeling Win 8 will be another Vista!
Look up the definition of obligated. If your arguement truly made sense, Microsoft would have already done that. But it probably doesn't hold true. In fact, it probably makes them less money, because people would hang onto 10 year old pieces of software.
Furthermore, I'd argue that you are being illogical because you are trying to use software on a platform that doesn't support it. If you want Office 2003, go back to a version of Windows that supports it.
If you are so concerned about how you spend your money, then maybe consider alternating purchases of of Windows and of Office; that ensures you don't run into these problems, and it doesn't require you to purchase BOTH windows and office.
An upgrade to Windows 8 on an existing desktop from a functional standpoint is almost entirely useless outside of a few small use cases; even if all your software worked, you gain nothing other than Metro...which is an App to launch other apps.
Considering how much you THINK Win7 and Vista sold poorly, I'm surprised you aren't still using Windows XP.
Tell me, why don't you complain about not being able to use Office 2000, or Office97 or Office95? Shouldn't a person who owns a fully legitimate version of Office95 still be able to run it today on Windows8?
Listen you have every right to keep using Office 2003, but make sure you use it with the Supported Operating System. Don't buy Office 2003 and complain that it doesn't work on the latest version of the Iphone OS.