A space colony is worth 2 VP. This may not sound like much but it adds up.
You can also build Space Colonies with your crew, which allows you to then boost a new crew to LEO instead of having to get them back from your factory.
Ah, I had missed the 2 VP for a colony. It would have been nice if that sentence had been bolded like the one earlier in the paragraph indicating all the other things that give 1 VP. That makes sense.
It does seem odd, though, that it appears you'd generally rather use your crew card than a colonist to colonize.