It is a fine tradition of strategic games that the AI wants to get all up in your space even when there is plenty of other better alternatives.
Alpha Centauri does it
Civilization games do it
they all do it as far as i know?
Galciv 2 does it badly.... It is quite amazing really,,, the colony rush, they all come for my worlds,, ok i deal with it as best i can. Then after that colony rush, many game years later i am still able to find many good un-colonized planets away from my area, amazing.