Quite possibly for the same reason that we aren't spread out all over the galaxy ourselves. The speed of light limit, and the enormous energies or time needed to traverse the galaxy put an enormous barrier to its exploration. Those barriers may be untranscendable, making them as difficult for others as they are for us. 42 posted by yendu bwam In our current physical definitions ('laws' of physics?), the speed of light appears to be a barrier and the temporal gel of present time appears to require traversing moments as if topping grains of present time along a temporal line with past at one end and future at the other end. It is not outlandish to believe there is a better perspective available, if we can discover the key to unravelling the foundational principle. Should someone discover a way to unify all the known forces, the key to transcending temporal limits as we now believe them to exist may be a natural outcome. Just as dimension space has three variable expressions (three functions), so dimension time may also have three variable expressions. Eventually, someone may devise a way to mathematically express this notion and equations will pour forth.
I also am not convinced that the speed of light will be a non-transcendable barrier. Yet there is really only scant evidence that it may not be. I've often thought that perhaps God designed the universe with certain physical rules and regulations - perhaps in order to prevent beings on their way to learning Godliness from destroying each other.