There are a bunch of themes floating around in these forums as well... Have you searched for "theme"?

Anyway, to answer your disbelief more adequately... Themes are rather complicated and time-demanding things to make -- aside from the need for a little artistic ability. And, most of the people who develop for tablets -- or even those who want to get a little deeper than just using the default apps and themes -- are not artists.

So, if you're a tablet user who is an artist... And if you also have the ability to design and create meaningful iconography... Then you can download and alter the massive PSD (Photoshop) file that contains all of the tablet theme art. Once that's done, you've got to learn how to use the ThemeMaker application in order to convert the theme into an installable package. Of course, then there's the process of uploading it to Extras, etc.

As you can see, there are a few barriers to easily creating a theme for the tablet.

But, many have, so it's not impossible.

Tim