Try standing up for a few minutes, being mindful of what your body does. You will probably find that you lean slightly from side to side or stagger very slight

Try standing up for a few minutes, being mindful of what your body does. You will probably find that you lean slightly from side to side or stagger very slightly, with your core having to be partly engaged all the time. Your feet are in the same spot, but your center of gravity shifts and the core is the only thing to counter that. Meanwhile, when you walk, the momentum of your upper body takes care of a lot of this, you just automatically lean forward and your feet get under you, offloading a lot of that adjusting from your core. Your center of gravity moves predictably and your feet can "plan" to get right below it in the next step you take.