Like when you send a .7z instead of a .zip or .rar to a friend or a teacher because that’s what your computer has installed and they’re like “Oh No, not one of those, now I have to install 7Zip” even though the same program that opens .rar also opens .7z I feel like people are way more annoyed when they receive a .7z
It’s much the same when I send .tar.gz / .tgz files. Folk get uppity about it not being .zip. I don’t bother with other formats purely because I know I can expand them anywhere without installing additional software.
As for .rar, I always view them with suspicion. Dodgy.
I’ve never come across a legitimate use of RAR, you are quite right about the link to warez/virus/trojans and other malware but it will never shake that association. As for Kaspersky, I trust that steaming pile of Russian spyware even less.