As with many eBay features, variations is another with quirks or glitches in the categories that support variations. The official list of supported categories is here
eBay.com USA http://pages.ebay.com/sellerinformation/sellingresources/multiplevariationslist.html
eBay.ca Canada http://pages.ebay.ca/help/sell/listing-variations.html
If you hunt for them (tedious to find), you will find categories outside the official lists with subcategory that allow variations. Even the toys category has one but it is not a useful category to list in because you may get policy violations for listing in the wrong categories. In other categories not officially supported, there are some subcategories that do allow variations and are very useful because the sub-category name is broad enough to allow many types of items.
This glitch has been exploited by some sellers in some categories for years. Which is how I found it by accident viewing listings. I could not understand how a seller had a variations listing in a category that was not in the official list. But they were listings in a sub-category with the glitch that allowed a variation listing. I only saw mention of this glitch once or twice over the years and even then it was indirect. Apparently few know about it. Those that do save a lot in listing fees.