If I start GUI emacs in OSX (not from the terminal) it does not know about my user environment variables.
The exec-path-from-shell
package mostly solves this, but while you can explicitly initialize specific environment variables, I can't see a way to initialize all environment variables.
I use environment variables to supply secrets to my applications, so I tend to have a lot of them and would prefer not to have to add and remove them from my init.el
.