Once you have installed the JSpeed plugin on your website, despite the fact that it's published automatically all options and optimizations are disabled and must be enabled based on your preferences and needs.
You should enable at least the 'Combine assets' feature in order to start having tangible results and speed improvements:

The 'Combine assets' feature is the most important and fundamental one. After that it has been enabled you can go further with activating other kind of optimizations.