It does not work on IE7 and has squared tabs on IE 8. And JQuery is required too, it is not installed on all websites. This version works on any browser without framework: http://www.xul.fr/javascript/tabs.php
The use of jQuery was to provide the functionality so you can see it in action. If I felt the need I could easily recreate the tabs on a series of pages that do not require javascript at all.
The only reason this might need javascript involved is if the tabs are changing content on the page without loading a new page, such as swapping out divs in a container.
I believe you are confused about design versus function.