If I read this correctly under Customizations: 95% use the "Status Bar" (though in which way is unclear) Yet the status bar was removed from the default UI with the argument that the space was wasted. (and replaced with the optional Add-On bar, taking up the same space)
Easier to have just provided the option to hide the Status bar for the 5%?
This was based on an old study from Firefox 4 Beta when the status bar was still on by default. (The study was in July 2010, when Firefox 4.0b1 was out; the status bar was replaced about four months later in Firefox 4.0b7.)
The "Customizations" number just means that 95% of users had the status bar enabled (i.e., did nothing and ended up with with the default setting) while the other 5% customized Firefox by disabling the status bar. It says nothing about how many users "used" (interacted with) the status bar.
Customization is not a good measure of usefulness. We know that 97% of participants never used the RSS button in the main toolbar in Firefox 4.0b1, but that doesn't mean that they all took the time to customize their toolbar to remove the button.
This may be due to settings carrying over from an older Firefox install. In my experience, Firefox has been quite good at not clobbering settings unless they decide to remove the feature entirely. I had forgotten they added "tabs on top" until I saw this, which actually reminded me to try it out.
Easier to have just provided the option to hide the Status bar for the 5%?