>>95118095Digging straight down means there's no way back up and you have no idea what the next block will be until you fall into it. Typically you'll just reach a cave and fall to your death, or hit lava and die or stumble on some enemy swarm with no escape route. Assuming you happen by sheer luck to avoid all that you'll eventually need to eat.
At the very bottom of the map is a layer of unbreakable blocks that effectively form the 'floor' of the world and that's it.
