Because, you know, scrolls is a pretty important aspect of the game.
I think a synonym is good enough. The Elder Scrolls games fall under the category of games which are often referred to by their sub-title (Skyrim, Oblivion, et cetera...), and so it is perfectly understandable what they mean.
I'm not sure a full renaming is in order, but I'll definitely put up a tag synonym between the two in the meantime.
I was originally leery about giving Skyrim this treatment, because it would necessitate renaming the rest of the elder scrolls tags.
That said, elder-scrolls-morrowind makes it in under the tag lenth (as does elder-scrolls-daggerfall), which I think are the longest names in the series, meaning that there shouldn't be an issue in doing all the rename requests you're suggesting.