Why is radial symmetry uncommon for land animals?

Land Animals have different appendages and can only be bilateral. Thus, land animals can move around. Bilateral symmetry is associated with cephalization, meaning that land animals have a central nervous system and sensory organs, being better able to detect predators and act accordingly. Whereas, most organisms with radial symmetry are sessile- they are marine animals that cannot move around thus radial symmetry is an adaptation to see their environment from all around. Also, the internal organ placement effects the animal's symmetry.