Why are animals called animals and plants not called still life?

Animals can actively move and walk, so they are called animals. There is a wide range of still life, and all objects that don't take the initiative to make movements and actions can be called still life, such as stones, grains of sand, buildings and so on.

And why are plants not called still life? Plants can be roughly classified as still life, but some plants have active ability, such as Nepenthes and Mimosa, so strictly speaking, plants are not completely still life, but they all have the same characteristics, and they are all "planted" in the adapted environment and take root and sprout. So they have a specific noun-plant.