Comment by GregDavidson

bash, ksh, zsh and a few other shells have the awesome feature that if you call them with a link named "sh" they accept Posix Bourne-shell syntax.

This means you can make them your /bin/sh system shell which will be used to log you in and your login scripts can then set environment variables for your whole session. This feature is something I count on.

Some system shells (not dash) also allow login scripts to export essential shell functions to the session environment.

I would love to use a nicer shell, fish, oilsh, rc, etc. but it's gotta provide this key Posix compatibility. The Posix Bourne shell language is pretty simple. This is not a big ask.