Agreed. For some commanders, Colonia is their bubble. Expansion should have been allowed from Colonia as well.
It will be.
But when you are running an experiment, because that is what this is, then why have it take place in two different places, especially if something can go wrong, as it already has?
I'm sure Colonia will be expanded upon.
Also, although there are so many stars, the developers have surely plans for empty regions and we can't just have player bases all over the place, for developers to then be forced to add unique things that much further away.
This way, expansion will go slowly and there are plenty of time for developers to make use of distant, but still nearby, systems.
For example, it's good that we have Guardian site nearby and we don't need to travel to the other side of the galaxy for that, and I highly doubt the developers would place guardian sites or such things in player claimed systems.