12-11-2018, 02:26 PM
Tarballs on their own don't offer compression (not that it makes a big difference when we're dealing with images) but more importantly, are not as user-friendly. Zips are supported on basically every OS out of the box and require no specialized software or know-how to use. It's the same reason we disallowed RAR and 7z files a long time ago - the user experience is important here and we want to make the content we host available with as few hoops to jump through as possible.