I think that's an advantage. You know what goes in and out, you can see where it's passed and used. It provides transparency and fewer accidental behavioral changes.
E.g. I had a really weird bug in a script, git seemed to break for no reason, until i figured out that some other script had exported GIT_DIR which pointed to the git top level directory. The name of the variable isn't bad if want to save that directory. But git uses GIT_DIR as the location of the .git directory it should look at when it is defined.
Using environment variables is kind of like using global state, it can often cause weird behavior at a distance without a clear path of influence if you don't know exactly which environment variables are used by all your scripts.
E.g. I had a really weird bug in a script, git seemed to break for no reason, until i figured out that some other script had exported GIT_DIR which pointed to the git top level directory. The name of the variable isn't bad if want to save that directory. But git uses GIT_DIR as the location of the .git directory it should look at when it is defined.
Using environment variables is kind of like using global state, it can often cause weird behavior at a distance without a clear path of influence if you don't know exactly which environment variables are used by all your scripts.