Why is it necessary to use a sprite for area effector?

It’s possible you can use a 3d object with it, albeit I’ve never used it in that way. The effectors are a 2d only effect. So you can apply 2d colliders and 2d rigidbodies to 3d objects and try using the effector like that. In theory it should still work exactly the same except you’re using 3d objects. Note that this will still work as if it was a 2D object.