One of the posters there put up a lengthy quote from a book about cavalry weapons in the post Civil War era, and I think that just about settles the matter as far as I am concerned, it makes a lot of sense -- the weapons were delivered from the factory blunt, and it was expected that the end users would sharpen them, but a lot of them ended up in the hands of troopers who had no skill in their use, led by officers who had no skill in their use, and these regiments tended naturally to make little to no use of the saber in combat. They simply never got around to sharpening them because it's a time consuming task, and they didn't care much for the saber anyway. I've seen a Civil War era sword that showed no signs of ever having been sharpened, and the "edge" was a full sixteenth of an inch thick. It would take a long time to grind away enough metal from that to put a good cutting edge on the weapon, especially on so long a blade (though the forte, near the hilt, was supposed to be left blunt, as it was used to parry not cut). Troopers and officers who had no skill with, confidence in, or desire to use the saber might well have simply neglected to do it, preferring to trust their pistols. This would have been even more true of cavalry during the Indian wars, where there was even less opportunity for saber charges, and sabers were often laid aside entirely and left with the baggage.
However those officers which did have some proficiency with the sword, and which imparted some of their skill to their men almost certainly did sharpen their sabers.
