When might marble not be a good idea?

In Turkey, marble is abundant. Walls, bathrooms, kitchens and even floors are often covered with the smooth, milky material. But I often wonder why public spaces, sometimes wet from rain, are made of marble. Case in point: this lovely small amphitheater. When it rains, out comes the "slippery when wet" cone, to be stationed neatly in epicenter. Still, very pretty.