Did you ever read about Optimization of website/blog through ordering styles and Scripts in head section? If you like your website load in browser as quickly as possible then you may have read in performance optimization tips that you should move all CSS files on top and script at last in HTML head section <head></head>.
If above lines, do not makes much sense to you then probably you have not read this documentation on Google.
The plugin will also collect different inline scripts to one place. Thus making the source code look better.
To check, if the plugin is doing anything or not, compare the Head section before and after activating the plugin.
(For reading more details discussion, follow the Plugin link on right side.)