Obsolete is really in the eye of the beholder. If ancient software on an ancient PC or ancient software on a modern PC allows authors to do their job, then these tools are probably not obsolete in their eyes. At least in the context of writing. Some people hold similar views of XP. Many more people hold similar views of Windows 7. Keep in mind: computers are appliances to many people. They won't replace their fridge or TV until it breaks down. They certainly don't expect the electric system to change, thus forcing them to buy a new fridge. They don't expect TV signals to change either, thus forcing them to buy a new TV, which is a good part of the reason why the transition from analog to digital took so long. (Even then, many people use some form of external tuner to get the job done.)

I'm not claiming that everyone holds that view. Clearly there are people who upgrade their TV to support the latest standards. There are also people who will buy the latest decked out refrigerator, rather than a basic model or a used unit. (Yet I suspect fridge upgrades for the sake of upgrading is relatively rare.) The same holds true for computers, probably to a much greater degree. Yet that much greater degree is largely due to the tremendous amount of progress in the technology. There are things that we do today that we couldn't do 30, 20, or even 10 years ago. Yet that is slowing down. The development phase of desktop computers has mostly stalled and even gadget lovers are bemoaning upgrading their computers because they'd rather upgrade their mobile devices. Yes, those are still computers. Yet people still treat them differently. In the long and mid-term I suspect that you'll find that companies dropping support for older desktop operating systems will be doing so at their own peril. This "upgrade your computer because it is obsolete" mentality will become as obsolete as some people claim that XP is today.