Climbing up on Salisbury Plain

I've got a desktop picture of Stonhenge, and it just occured to me... every picture I've ever seen of Stonehenge ("one of the biggest henges in the world") has it backed by a moody gray sky.

Is that the result of photographers looking for the ghostly feel, or is it just that a sunny day over Stonehenge is rarer than Merlin giving interviews on Sky News?