Here's why:

* Energy Source: Plants obtain their energy directly from sunlight through photosynthesis. They don't need to actively search for food like animals do.

* Movement: While plants can grow and shift their parts, they don't have the ability to move around independently. Their movement is mostly limited to growth and responses to stimuli like light or gravity.

This is in contrast to animals, which require a lot of energy to move, hunt for food, and maintain their body temperature.