Ubuntu, being a hunk of an OS, is not giving out Ads! I mean, See Microsoft for instance, Whichever Blogs or Websites you Visit you get a Nice girl holding a boquet of flowers and saying Windows 7, Beauty and Brain.
In My country, India, Ubuntu is so unknown to Non-Geek people that they wonder if it is some Alien Product, Why doesnt Canonical think of it? Doesnt an Ad in some Newspaper Exponentially increase its users?