RAR files are already common enough for most Mac users to come across one at some point, mostly when they need something fast from inside it. It could be a project folder, a set of images, a document pack, software resources, or archived materials sent by someone using a different system. The annoying thing is not the file per se; it's rarely, ever the file. The frustrating part is when the Mac workflow slows down because the archive cannot be opened as easily as expected. You have a desire that people have for the same thing here: open the archive, extract the files, see what's inside, and move on. Anything that is more complex doesn't feel absolutely needed very quickly.