I don't think that's an excuse. As mentioned in other posts, there is an Add-on for vertical tabs: https://addons.mozilla.org/en-US/firefox/addon/tree-style-ta...

It can't hide the horizontal tabs though because of the strict rules imposed on FF extensions, so you have to hack around it yourself as described here: https://github.com/piroor/treestyletab/wiki/Code-snippets-fo...