That attitude is why Windows is around 90% market share, and Apple is under 10% share.
The operating systems should remain compatible, unless there's clearly a benefit to the end user to justify an incompatibility.
As an example - one of my most frequently used tools is TeraTerm, a telnet/serial port terminal app for windows (XP's telnet client sucks).
The latest version that I have was built in March 1998 - but it installs and runs without problems on my 64-bit Vista systems. Some of the DLLs were built in August 1996.
I wouldn't go as far as to suggest that is the sole reason Apple is under 10% share given it ignores the market trends all the way back to 1995 and the causes thereof, but I would agree it is irresponsible of Apple to cause software to break. I too have software for my Windows computer dating back to 1999 and using Windows98. When I built my new PC a year ago, I installed WindowsXP and ALL and I mean ALL my software from 1998 onward to today works in WindowsXP.
SOME of the Mac software I have here from 1999 works on the upgraded PowerMac I'm using, but only in Tiger with Classic running. None of that early software functions in Leopard on this computer or on my brand new MBP period. Many apps from the Tiger era even had problems in Leopard. Leopard proved early on it was slower and less stable than Tiger. Some of the speed losses have been reversed by 10.5.6, but not all. Stability does seem much improved, at least. But I believe it was irresponsible for Apple to release Leopard before it was ready. We should have seen 10.5.0 about 6 months ago (one year after it was actually released) and a SLEW of problems could/would have been avoided. There was nothing wrong with Tiger that it couldn't have continued on another year. In fact, it would have received some nice updates if it had and I might have better Bluetooth features, etc. in Tiger today (Apple simply stopped all updates to Tiger save security ones including camera support, etc. Microsoft continues updates to a Windows operating system several years after the new operating system is introduced. They don't just abandon it overnight like Apple does. Apple COULD have included Classic support in Leopard for PPC users, but once again, it chose to break all prior software compatibility. For a platform with so little software to begin with compared to Windows, it seems unconscionable to me, but then that's Steve for you.
On the other hand, most software for Linux breaks after revisions to the operating system as well. The only major difference is that it's mostly open source and so you can just recompile and everything is usually well again and if not, someone will usually fix it if there's any interest in that program. The same cannot be said for things like GAMES and games are the primary form of software that cannot and will not be supported by Mac OS. It's unreasonable to expect software companies to bother to update games that are no longer selling for an operating system (hence the term Abandonware) and it's unfortunate that such software isn't made open source so others CAN fix it, but that's not how the world works and so most Mac games don't work on newer Mac operating system versions.
Of course, most responses in this thread will be by fanboys and they will tell you that Apple MUST do what it MUST to continue to make OS X the best operating system in the whole wide Universe!!! Most of those people, though are clueless fanatics and hence the term fanboy. Microsoft, the kludge of operating systems that it is does a pretty good job of maintaining backwards compatibility. While problems do surface between hardware, etc., given how MUCH hardware it supports, it's still a pretty good job all in all considering. If Windows only had to support the handful of hardware variations that Apple supports, it would be darn near problem free as well. But that's the difference between 90+% and 8-9% of the consumer market.
I use OS X precisely because it's a small market and uses Unix type cores. This makes it stable and highly unlikely to be attacked by malware and viruses (the combination thereof). Thus, it's the machine I want to use when shopping or banking online or to drive a 24/7 house audio/video system and that sort of thing. That it's more friendly to use 'most' of the time than Windows doesn't hurt either. But it also means I keep a Windows machine around as well for gaming and software you cannot get for the Mac. Yes, I could install Windows on my MBP and have both on one machine but then I might open the Mac side up to potential issues as well and I'd have to start virus scanning (takes FOREVER these days given the large hard drive sizes, etc.) on the laptop and I'd rather not, really.
