Não é avaliado toda vez que você usa tcsh ou ksh . Então provavelmente é avaliado apenas por zsh .
De aqui :
zsh
As always, zsh is very flexible. Startup files are read from the directory named in the ZDOTDIR environment variable, if any;[6] otherwise, from HOME. All shells read the global /etc/zshenv and your .zshenv files. If the shell is a login shell, commands are read from /etc/zprofile and then your .zprofile. Then, if the shell is interactive, commands are read from /etc/zshrc and your .zshrc. Finally, if the shell is a login shell, /etc/zlogin and your .zlogin files are read.