- Player Freedom
This is what allows the player to build and destroy live in these games, altering the world to a degree that's more or less unprecedented prior to this. This alone is powerful enough that there is an entire genre of games with this as their central feature. Minecraft is a solid example of this. Minecraft became wildly popular as a game before its feature set really included anything else.
- Developer Freedom
The other expression of freedom is on the developer side. Due to several of their basic characteristics, voxel/cube-based games lend themselves quite well to procedurally generated content. This is of particular benefit to smaller studios that might not have the manpower to put out a lot of handcrafted content. A solid world generation algorithm can let them focus on interesting gameplay and new features, rather than the hundredth QA run through the game's intro level.
So what do you do with all this freedom?
I don't know what you do with it... but I'm doing this.
More coming soon.