Decades Ago, a Brick Factory Used to Be Located Along

Decades ago, a brick factory used to be located along a river.Waste materials and faulty bricks were piled along the banks of the river, and some of them fell into the water.Years later, some of these materials were removed.The bricks were still recognizable as bricks, some with the manufacturer's mark clearly visible on the front, but the edges and corners were rounded over.Why were the edges and corners of the bricks so rounded over while the faces of the bricks were largely untouched?