system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Shouldn't black holes eventually swallow EVERYTHING?

ELI5: I never understood why black holes don't "snowball" in to galaxy swallowing super-giants, especially given the amount of time they are around. I figure the more it swallows, the bigger it gets, the bigger it gets the more things are attracted to it, creating a universe sized cataclysmic tear in the fabric of space-time. Tell my why that doesn't happen.
gpt
Black holes aren't cosmic vacuum cleaners that just suck and suck and suck. Things orbit around them just like our moon orbits the Earth, and the Earth orbits the sun. The difference is a black hole is so big that once you get too close you can't escape its pull no matter how fast you go, you fall into it. Galaxies are really big and mostly everything in one is much too far away to just fall into the black hole. 

In short, space is really big and mostly everything is really far away, even for things as big as black holes.