You are probably doing nothing wrong. Not all of the packages in Synaptic are
programs. Some are libraries and as such would not be executable or have a menu
launcher. If it is a program, but runs from the commandline, you won't get a
menu launcher either. If the program is not completely installed you may not get
a menu item because the script has not completed. In rare cases you may not get
one if it is a KDE program, but for the most part you get KDE programs showing
in Gnome.

Not being familiar with the ones you named I can't tell you what they are and
whether you should have got a menu launcher or not.