Potato Onions taste just like any other onion, but do not look or taste anything like potatoes. The common name simply reflects their similarity to potatoes in the way they are planted and grown, and how they multiply. Potato onions and shallots are almost never multiplied by seeds, but must be multiplied by planting a bulb in the ground, much the same way you would plant a potato to obtain more potatoes.
That’s why.