Why should you update your WordPress site? If you don’t, you are subject to hackers.
The folks behind WordPress are pretty darn good about keeping up with breaches to WordPress, but you leave yourself open to trouble if you don’t update as soon as is possible. Read more about it in this article: http://lorelle.wordpress.com/2012/08/26/update-wordpress-now-reuters-hacked/.
WordPress has become very popular, so it grabs the attention of those who would wreak havoc. I wouldn’t advise messing with it. Keep your WordPress and plugins up-to-date. Update now.