Why does nothing change when I attempt to restore a backup?
This sounds like a bug of Backup and Migrate module, since file_directory_path() no longer exists in Drupal 7.

So instead of file_directory_path() you should use:

file_stream_wrapper_get_instance_by_scheme(file_default_scheme())-&gt;getDirectoryPath()


or:

variable_get('file_public_path', conf_path() . '/files')


So please upgrade your module to development version (but it's not fixed yet at time of writing) or use this patch available at: #2618516 - Fatal error when restoring "Entire Site" which goes like:

--- a/includes/sources.archivesource.inc
+++ b/includes/sources.archivesource.inc
@@ -208,7 +208,7 @@ class backup_migrate_files_destination_archivesource extends backup_migrate_dest

       // Move the files from the temp directory.
       if ($filepath &amp;&amp; file_exists($filepath)) {
-        _backup_migrate_move_files($filepath, file_directory_path());
+        _backup_migrate_move_files($filepath, variable_get('file_public_path', conf_path() . '/files') );
       }