Usefulness

Portability    easier to adapt if the script is moved to another location,
                    or if directories are renamed!

Security
    the script does not reveal your directory structure.

Error reduction    reduces errors from misspelled or miscased paths.

"By default, it exports the functions cwd(), getcwd(), fastcwd(), and fastgetcwd() into the caller's namespace.  Each of these functions are called without arguments and return the absolute path of the current working directory."