Create a Gradient far away from the camera in material M_Water_Lake

what is the role of ‘Create a Gradient far away from the camera’ useful in M_Water_Lake?
After a few steps calculate , it just get a node same as constant 3Vector.
And when I try to using constant 3Vector to replace the whole process of ‘Create a Gradient far away from the camera’, the material still looking good.
So why they add ‘Create a Gradient far away from the camera’ to this material?

I did not look at material, but most likely, for artistic purposes, such as reducing noise or making normals more flat in the distance.