Because to ship screensaver output over vnc takes a lot of CPU
and network resources. IMHO this should not happen by default,
because newly setup machine with a few users running vncserver
hammers the machine.
Just as true for non Vnc screensavers
If they want to setup screensavers explicitly, fine, but
at least you can lart them for that :-)
It sounds to me more of an argument for using 'blank' as the
default screensaver except on localhost ?