What's with the Sunglasses ?

Why, oh Why do people wear sunglasses when it isn't sunny ?
It never ceases to amaze me !
You never see people walking down the street with umbrella's up when it isn't raining so whats with the bloody glasses ?
I see people every day on the tube in London wearing sunglasses. What are these people trying to hide ?
Take it from me,

You DONT LOOK COOL YOU LOOK STUPID, stop it now !

R