This procedure (for Debian, Ubuntu, and derivatives) is useful when need to create a template, and your host doesn't have that suite's script (in /usr/share/debootstrap/scripts). This situation can be caused because happen when your host and your next template are from different distributions, or because when your host is an older version than the next template you want to create (for example, creating an Ubuntu 10.04 template in an Ubuntu 8.04 host).