You should ask yourself why/how Le Chatelier's principle works to begin with. The most general statement is as follow: if a system is at equilibrium and some stress is placed on the system, the system rearranges to relieve that stress. If you increase the pressure, the system will want less gas to alleviate that stress. If you increase volume, you're effectively decreasing pressure so the system will want more gas to relieve that stress. Why does this only apply to gases? Well, think of a reaction that is liquid phase only. Increasing pressure on a liquid doesn't do much to it because it's already in a condensed state. You're not stressing it as much as a gas. Even if you were stressing it, going the other way in the reaction would just produce another liquid - it wouldn't relieve your stress much. That's the simplest way of explaining it.
