pressure at the same level inside the fluid is same in all direction. pressure inside liquid only depend on the depth.
if the dimension of the box is quite big, then the pressure at the top surface may vary from pressure at the bottom. but pressure is always due to force perpendicular to the surface.
where as for solid, pressure always acts perpendicular to the surface.
so there can not be different directions for pressure, which may effect the motion or dynamics of the body. it is force which is responsible for that. so force is vector quantity.