There are plenty of reasons to choose Debian, but having the most recent versions of your favorite applications is not one of them. Software updates trickle down to the stable version of Debian very slowly, which means that packages in the distro's repositories are likely to be a few versions behind the current releases. digiKam is no exception: the Debian stable repositories contain a version of digiKam which can be considered outdated.
This is a companion discussion topic for the original entry at https://digikam.org/news/2013-10-14_install_the_latest_version_of_digikam_on_debian/