Since macOS Catalina, zsh has been the default. bash switched to GPLv3 awhile back, and to avoid licensing issues, Apple never updated bash past 3.2, which was

Since macOS Catalina, zsh has been the default. bash switched to GPLv3 awhile back, and to avoid licensing issues, Apple never updated bash past 3.2, which was already well over a decade old at the time. https://thenextweb.com/news/why-does-macos-catalina-use-zsh-instead-of-bash-licensing https://thenextweb.com/news/why-does-macos-catalina-use-zsh-...