The reason being that you will have a better view of space/planets around you while flying and its more realistic overall to have a bit fewer astroids.
The way this mod works is it modifies the speed at which this effect is triggered, making it not show unless the player reaches what I think are impossible speeds. But if it turns out higher speeds are possible, Ill update the mod.
This modifies the following files:
MINIJUMPSPEEDLINES.SPEEDLINE.MBIN
MINIJUMPSPEEDLINES2.SPEEDLINE.MBIN
SPACE.SPEEDLINE.MBIN
SPACE2.SPEEDLINE.MBIN
SPACEBIG.SPEEDLINE.MBIN