Why do you start boiling potatoes in cold water ?

"Why do you start boiling potatoes in cold water instead of adding them to boiling water?"

When you add potatoes into boiling water, the outside of each piece gets mushy by the time the inside is cooked. Or, to put it another way, potatoes added to boiling water cook unevenly. If, on the other hand, you place potatoes in a pot of cold water, the water and potatoes heat up together, and the potatoes cook evenly inside and out.