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
Never use 7z, because I do design work for a living and sending things to clients should be as trouble-free as possible - lots of corporate setups don’t allow additional programs to be installed, so zip files are a baseline for things that everyone, anywhere, can open. People have enough trouble trying to understand a WeTransfer download link, let alone some bizarro file format that could be flagged by their antivirus.