Because i run this program as an ordinary (non-root) user, i do not have permissions to create subdirectories in system tree (the /Library... and so on). The configuration written in system tree will be common for all users on this computer (me, my wife and my daughter - all my family uses this computer from time to time) and can be overriden by them. The configuration for particular user should be saved in "$HOME/Library/Application Support" - generally on unix-like systems it's not safe to assume the user can create files and directories anywhere outside his home directory.