[spoon]

The main "gamey" reason I consider taking rock/none (or ice/none) is the ability to find a planet with two moons, and build 3 spaceyards, 3 Fleet Training Facilities, and 3 Ship Training facilities in that sector.

The disadvantage is that you have to rely on capturing/trading other pop types to maximize Gas Giant colonization (when you get that tech). This can be a hefty disadvantage, depending on the game setup and the disposition of your neighbors.

-spoon