No reason? Changeset comment provides an expilcit reason why the tag was removed. It's value really is outdated, and misleading in relation to current name. If it shouldn't be removed entirely then somehow at least it should be made clear that the value is associated to old name. I don't know if there is a good way to make this clear. Note that OSM generally doesn't include historical data anyway (with a few exceptions).

You also reverted changeset/160690969 but again MourningVulture actually did provide an explicit reason, contrary to what you claim. This etymology is for the entire road and so it does seem reasonable to add it to the relation instead of repeating it for each road segment.

It seems to me you reverted in a sort of careless manner, without checking what exactly you revert, and so MourningVulture edits should be restored (apart from missing highway tag for one road segment which was probably by an accident).