My article a while back on Why the Disk Management snap-in reports my volume as Healthy when the drive is dying gave the low-level explanation of why the Disk Management snap-in does not incorporate SMART information: because the Disk Management snap-in is concerned with volume partitioning. DWalker59 noted that the use of the word "Healthy" carries more meaning than the authors of the snap-in intended. The authors of the snap-in assumed that everybody knew what the Disk Management snap-in was for, and therefore everybody know that the word "Healthy" applied to the state of the file system.
I never said that this was a good situation, and commenter Dog interpreted that since I didn't say whether this was a good situation or a bad situation, I must be saying that it's a good situation. Actually, since I didn't say whether this was a good situation or a bad situation, this means that I'm not saying whether this is a good situation or a bad situation. The article was posted in the Tips/Support category, which is about helping you cope with the frustrations of using Windows, not about passing value judgements on what is good or bad. The point was not to say what is good and what is bad, but merely to say what is.
Dog thinks that the blog would be far more interesting if I shared my opinion on things. Actually, I try not to share my opinion on things, because the Web site isn't about opinionating on Windows; it's about practical programming on Windows. Practicality means that you have to set aside whether something is good or bad, because it's there and you have to deal with it regardless. If you want opinionated writing, check out Robert Scoble or Michael Kaplan. Dog also assumes that Microsoft's PR department has told me not to opinionate on things. In fact, they haven't told me anything one way or the other (yet, and I hope it stays that way).
(I found it interesting that Dog claims that "the act of reporting on [something] gives the appearance of support unless otherwise stated." I wonder if people who cover armed conflicts have to add an explicit statement along the lines of "killing is bad" so Dog won't think they support people shooting at each other.)
From a historical standpoint, the situation is a bit more understandable. After all, the Disk Management snap-in was written long before support for S.M.A.R.T. information showed up in Windows Vista. You can't fault the original authors of the Disk Management snap-in for not taking into account data which didn't exist yet.
As for why the Disk Management snap-in didn't incorporate this information when it became available, this assumes that there were resources available to do the work. Disk Management is a very old snap-in that hasn't changed much since it was first written. My suspicion is that maintenance of the Disk Management snap-in is assigned to a group which has as its primary goal some other part of the system; they were just given Disk Management because it has to belong to somebody. Consequently, that group has very little incentive to make any changes to Disk Management at all, and certainly has very little incentive to add features to it.