Because in Geological terms, it is an open booock to the history of the natural world that we inhabit.
I don't know who you think "they" are, but humans did not create the Grand Canyon.
yes, they do.
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Because it is a historic landmark in science and it was a beautiful masterpiece.
the grand canyon
a Grand Canyon is nothing but a big erosion.........
Copper Canyon (Spanish: Cañon del Cobre) is such landmark.
It is a Canyon as in the Grand Canyon.
Black canyon
The grand canyon is grand
Not certain who is the "they" you are asking about, but no human had any choice on making the Grand Canyon a big thing. It was already big when the first humans saw it about 12,000 years ago.
Le Grand Canyon.