Am I missing something or why is no spy/track blocker included in the browser bundle? I undestand that add-ons may weaken the anonymity/privacy but aren't the example add-ons below not trusted?

e.g. Disconnect https://addons.mozilla.org/en-US/firefox/addon/disconnect/

or EFF's Privacy Badger https://addons.mozilla.org/en-US/firefox/addon/privacy-badger-firefox/