Choosing to install a particular desktop environment when you want a "graphical environment" is only a matter of convenience : proposing GNOME from a CD install is getting harder because of the size of new versions. Several ideas were proposed : changing the default DE in tasksel, changing the compression scheme for .debs (using LZMA instead of bzip2), or even dropping CD installations IIRC (keeping just CD and USB netinstalls, and DVD installations).