So if you want your distro to package them, ask your distro to package them. There is not much difference between extensions.gnome.org and 'ftp.gnome.org' in that. It is provided on a site, but it is up to the distributions to package it and keep it up to date.
The difference in this case is that extensions.gnome.org provides an easy way to avoid the distro and see what has not packaged.
I get the impression you think providing a easier non-distro method is somehow a bad thing done by GNOME?