When the scene was first played gravity was enabled so the initial drop kept the ball going even with it off. If you turn off gravity the object can still be affected by other physics objects, it just won’t fall to the ground like it typically would. Give it a try, add two spheres with rigidbodies. One above the other. Place the one at the top to use gravity and the other to not use gravity.
When the top sphere hits the second ball it’ll push it out of the way. Think of these objects as if they were in space, they can still be moved, but they’re not affected by gravity. If you don’t want them to move at all you can use “Is Kinematic”, which tells Unity that you plan on moving this object on your own for something like an animation.
