Part of the goal for the desktop livecd is to be as universal as
possible - this means supporting as many languages as possible.
Well not just fedora-live-desktop but all main spins IMHO.
That is why we have @fonts and @input-methods in fedora-live-base now.
There is no reason to install all Korean fonts for example for all users.
(And unfortunately that is what we are doing in the F10 Desktop spin currently :-/)
The lang support groups are just duplicating @fonts and @input-methods
and pulling in packages that should be optional for general users.
As a side benefit, it avoids us having to host 20 language spins
In fact largely the local spins are just removing fonts and input-methods and adding some
of their own optional packages: which is exactly what the language support groups are for.