Lua is widely used in the game industry. From independent games (Aquaria) to AAA titles (Civilization).
The core reason? I would say because it is easy to learn and easy to incorporate into your games. But the same could be said for Python, I'm sure. Scripting, in general, isn't difficult. I think the real reason you should go with Lua is because it's proven which results in much more resources out there for you to learn from.. If you feel like experimenting with something outside of the norm then I would start messing with another language.