For that you would have to ask Google. But you have alternatives and you can override compatibility and use the Extension. See https://support.mozilla.com/en-US/questions/841081

The Google Toolbar "will not be supported on Firefox 5 and future versions." <br /> http://googletoolbarhelp.blogspot.com/2011/07/update-on-google-toolbar-for-firefox.html http://www.google.com/support/toolbar/bin/answer.py?answer=1342452&topic=15356%29 The Google Toolbar '''7.1.20110512W''' version does work pretty good in Firefox 5.0 by using the Compatibility Reporter extension. But not every feature works 100%.<br /> https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/ http://googlesystem.blogspot.com/2011/06/enable-google-toolbar-in-firefox-5.html