Why do plant cells need a cell wall but animal cells do not

Cell walls are rigid which gives plants their shape. Animals have only cell membranes which allows animals to be flexible as animals are moving organisms. Plants, on the other hand, are sturdy and upright and are sessile organisms. Cell walls allow plants to grow upright as high as their maximum height and to be sturdy enough to survive harsh environments.

Only algae, oak trees, and bermuda grass produce atp by photosynthesis i am almost positive