In the good old days, we need RAR so we could split the file into multiple floppy disk, now simply known as the Save Icon. We also prefer it over zip simply due to better compression ratio. I wonder do we still need these trade offs or we could simply go back to Zip or other self extracting compression format. I don't think RAR is even natively supported on Mac.
.rar should be avoided since support in open-source extractors is rare (to my knowledge, the sole implementation comes from The-Unarchiver, `unar`). .7z is usually the way to go if not doing something fancy like casync.
I do want to point out that for transmitting compresed files 7z is fine, but as a longer term backup format rar has a lot of functionality that makes it convenient (built in verification, parity generation/repair, support for all the extended filesystem attributes)
I've seen "arrow over cloud" icon as a save icon in one of the web apps we use, and I was deeply offended :( for so long it has been the floppy disk icon