Gases can be crammed into small spaces with ease?

Gasses take that shape of the container it is in. It is not space efficient to store gasses in their gaseous state as the atoms are loosely together and that leaves a fair amount of empty usable space that is wasted. To make it more efficient to store gasses are pressurized so that the atoms are forced to lump together more closely than in the gaseous state. This creates the gas to condense down into a liquid. Making it far more efficient for gasses to be stored so long as the pressure is maintained.