But you need to understand that Firefox was created as the Stripped down version of a Browser to keep browsing fast. The user then comes along and adds in what they NEED. So the user only has 3-4 things which they use slowing down the browser compared to 10-15 things which are not entirely used...
I think the Firefox should have a lot of the good things ready to be installed at the click of a box. BUT that doesn't mean they are already installed, just disabled.