I thought about this too and I think at one point they agreed with you since originaly the star field was going to be the only tourney legal one, however I think they quickly realized that as long as everyone has the same chance at expericne with both maps then niether player has an unfair advantage.
I'm pretty sure that they made that change because they actually wanted to sell some of those Deathstar mats. As awesome as they look, if you couldn't use them in tournaments then I'm sure most people would opt for the starfield one.
