Interior design are like contractors -- they can make structural changes to physical structures as part of their course. I don't see it as at all ridiculous that they need a license any more than for general contractors. I frankly want to know that they've done some studying before they cut into my walls.
It would be bullshit if you were referring to interior decorators, but I don't think there's any certification or licensing to become an interior decorator unless you join an association or club that requires it.
(I think this was reversed since the story)