That's actually surprising to me. Being in the North Atlantic, I would have thought thunder storms would be common. I lived in LA for 5 years, and I definitely missed thunder and lightning. If I were going to space, I'd bring rain/thunder/lightning sounds to listen to like we've seen in sci-fi films even more so than the ones with cricket sound tracks.

I live in Dublin, which is shielded from the worst storms. Still, the weather patterns are not conducing to thunderstorms and lightning strikes average to around 10 per day over the whole island.