Well, actually, there is an apparent reason: To attract tourist dollars. At least that's the plan according to the propaganda.
Which puts it right up there with 1000 other goofy roadside attractions peppering America. Honestly, it's the only damned charming thing about our country. How many times have foreign heads of power convened to discuss whether they're fed up with America's shit enough to nuke us already, and we were saved by somebody raising their hands and going, "But that would destroy the world's largest pencil in Baltimore, Maryland"? And the United States was spared once again.