i'm sorry but as a windows pc technician i have seen updates destroying windows installations, that is why most users never update their systems and they specifically set the system to never search for updates
Having helped a few friends get their Windows boxes into shape recently, it's hard to believe how long it takes to put all service packs on XP. But certainly I have recently seen a few machines which were never upgraded since being purchased many years ago.
In the old days, it was considered proper to re-install Win95 once a year - otherwise it ground to a halt. That changed with registry tools being widely available.
But having fixed up machines which were upgraded through several versions of Windows - a clean install was the best solution. Registry tools and mft purge and PerfectDisk defrag work to a point - but a failed Symantec or other antivirus always came back to haunt.
In the past, when new version of PCLinux has arrived, I must admit that I've installed it on a new partition and kept the old version until I felt good about the changes. So in a strange way - I've always supported fresh install, but for my own reasons.
Since Vista, reinstall has meant first formatting the partition. I'm curious about whether most new Windows machines come with a OS partition and a data partition. The current state of advice with regard to compromised systems is to format and reinstall the OS, due to rootkits. In my own experience with my grand-kids machine, Vista failed due a power outage. I was surprised that I couldn't get around the issue - since I could read and backup data using Linux. Later I was able to re-use the drive, too - after getting it to mark bad blocks.
It does appear to be a big pain, helping people to backup properly then re-install. I'm aware of the time required. But many people will not have backed up properly - despite the fact that these days everyone has photos on their drive. It's surprising how many computers have CD/DVD burners which only read DVD - so backing up might require a new DVD burner, given the size of digital pics now.
I'm in the process of backing up my main drive now - onto a external backup drive, and DVD. I'd put it off for a while, which is always foolish given today's terabyte drives. So while I haven't lost anything, I do feel foolish for taking silly risks.
Most Windows users have to be reminded of why to back up, and educated in how to do so. So I'd bet that M$ would go through any upgrade kludge in order to prevent people complaining of losing data because they failed to read the instructions before re-installing.