not2easy - 11:41 pm on Feb 18, 2013 (gmt 0)
All category listing pages are no-indexed but then still included in the sitemap.xml This isn't a WP install but I believe this is also the default (or a recommended, anyway) setting in some of the WP SEO plugins.
The reason WP SEO plugins allow the option to disable indexing category pages is because that often is only an alternate method of reaching those pages or posts and they could be seen as duplicate content, not because they are thin. Categories in WP are used differently than the way you are using them, generally a WP category is a virtual page listing posts or pages that have been tagged with that category and they may also be listed separately under monthly or yearly archives. The default behavior of WP gives many ways to find the same content, but a static site doesn't usually have that problem, unless it was structured to find the same content multiple ways.
As mentioned, if your category pages are the way visitors find the pages they list, then you probably do want them indexed.