When you jump down from a table why do you bend your legs rather than keep them rigid?

If you kept your legs straight whilst jumping etc, You could end up doing serious damage to them such as braking or jarring a bone. From a high enough height, even forcing your legs to go into your stomach, instantly killing you. Bending your legs softens your fall, keeping you safe.

Have you ever tried it? Jumping whilst also trying to keep your legs straight? It's like, a natural reflex. It just happens.