There would be nothing to make a base for a colony, and it would be unlikely you'll find a group of people in level 0 so that's probably why they got rid of it, but i think its why it should stay gone.
I don’t think the removal of colonies and outposts from level 0 was meant to imply that there were none, just that they were not listed on the page. I recall that there was a discussion a long time ago where it was decided that colonies did exist on level 0.