So far there are only three questions tagged with iupac and it doesn't seem like any of them need it. Even if you think that the tag is helpful for these three questions, the fact remains that, well, it's only three questions.
I don't have statistics, but I am fairly confident in saying that the most common usage of iupac arises due to newcomers asking nomenclature questions. This means extra retagging work. Not that it's difficult work by any means, but my point is just that there is a drawback of keeping the tag around.
Since this is a website for chemistry concepts and not about the workings of IUPAC, I don't really see any legitimate case where we would have a question about IUPAC. As hBy2Py wrote more than a year ago:
Appears it was originally intended as a tag for questions about IUPAC itself... are such questions even on-topic for the site at present? My impression is that they're not.
I think not too. Sure, we can have questions about why they decided to adopt some rules (e.g. the three currently tagged questions), but that is appropriately covered under nomenclature or terminology or whatever, as it is actually asking about the rules instead of the body.
Could we get rid of this tag?
Edit to clarify my argument for getting rid of the tag
Let's look at the three questions currently tagged with iupac. Two of them are asking about provisional element names, which are covered perfectly well by [elements] + [nomenclature]. One more is asking about the 2013 Recommendations for organic nomenclature, which is covered perfectly well by [organic-chemistry] and [nomenclature].
None of these fall under the stated scope of [iupac]. It reads, and I quote,
"This tag should be applied to questions about the organisation IUPAC. For questions about nomenclature, the appropriate tag should be applied."
However, these questions are asking about IUPAC rules, not about the organisation. So, to me, it seems that these questions do not satisfy the very first stipulation.
On top of that, the usage of [iupac] on these questions clearly directly contravenes the supposed rule that questions about nomenclature are not supposed to be tagged with [iupac].