Comment 9 for bug 351293

xubuntu-desktop is a meta-package, that is, it pulls in all the packages needed to make xubuntu. After it does its job, it can be removed without changing the system. So, it is not removing all the packages needed by Xfce, but only the meta-package. 'dpkg -l xfce* ' will show the packages for Xfce, and 'dpkg -L xfce* ' will show the files and their locations on your system.