Pages – Won’t contain author information because these pages are meant to be more official of the website as a whole and static, not to an individual.
Posts – Will contain author information as posts are considered writings, postings, articles, update etc from a specific individual.
This is standard for most WordPress themes and best practice. Also see http://support.wordpress.com/post-vs-page/
With that said, would you like to customize pages so that they do contain author info?