Say you make something out of 150 tanned hide, 15 silk, 30 amber and a Rune of Superior Vigor. Wouldn't it be nice to get a portion (say 2/3rds) of each material back and the rune? The sum of those materials is worth a small fortune, so it would be great if salvaging your own things was... less painful than it is

The same applies to weapons. You put 2 perfect upgrades on a customised weapon and then later want to delete the character or give the upgrades to another character. It would be good to salvage those upgrades and some of the weapon's materials. In the case of collector weapons (which can't be salvaged), it would be nice to be able to at least salvage the upgrades back.
Another option would be to have a kit that can remove runes and upgrades without damaging the item.