Why is the lattice not bending the object like the tutorial?

[loserlearningblender (Loser)]

I was watching this tutorial and found that lattice thing sound interesting, so I tried to do that (but not creating the whole shield; I just use a thing cube, instead).

Modeling an Ornamental Shield in Blender 2.8 - Beginner Tutorial

I followed what he said and I got the lattice bent as his, but when I applied the lattice modifier to the cube, the cube did not bend like that. Only its two side faces were slightly bent. Why is it so?

[a59303]

Are there any subdivisions on the mesh? If not, go into edit mode and add some vertical loop cuts ctrl r in the mesh.

[Travisty (Travis O'Brien)]

There just isn’t enough information to create the ‘bend’.
As mentioned earlier, adding some loop cuts solves the problem.