Simply because Joomla CMS is well known and well used content management system. Web sites created with this software are also targets for attacks from either simple defaced website through to redirected URLs.
Upgrading and ensuring latest version of core components and addons are the prime prevention method for web site hacks. However there is still the chance a site will be hacked.
NZJoomla has considerable experience with restoring hacked Joomla sites and harding up sites to prevent future web site hacks.
If you need your site restored contact us now.