During the latest ISC, the effects team mentioned that space dust exists to give you the parallax of movement. Of course, in the real world, all motion in space is relative; there is no preferred frame of reference, so when you aren't accelerating you have no sense of motion at all. Space dust are spots of light spread out across the whole system, standing still relative the sun. Our motion is measured in relation to this space dust, so when we are standing still, we are standing still relative the space dust, and when we are moving, we are moving relative the space dust. This means that the space dust imposes an artificial frame of reference throughout the whole system, centred on the system's sun. However, with such a frame of reference, we can never have orbiting planets. If we did, the planets would need to be moving through the space dust at insane speed (Earth orbits at 30 000 m/s) just to get around the sun within a year. That fixed frame of reference also makes it completely impossible for a ship to land on a planet, because you will either have to fly super-fast, trying to catch up to the wildly orbiting planet, or you would need to stand in the path of the planet's orbit, hoping to survive when a literal planet's worth of mass barrels down on your ship, like a million, million freight trains crashing into you. All of this is of course completely unrealistic, totally breaking immersion. Space just couldn't work that way.