Very stupid question, but why does the potato plant produce the potato bulb? What's the purpose

There are no seeds in the potato bulb, but it's high in energy, so evolutionarily speaking, it seems like a waste of effort...

1. Potatoes produce seeds if they flower and are fertilized.
2. Tubers (not bulbs) are an overwintering structure. Potatoes are perennials, so the tubers help them survive the winter or other times of stress, like drought.