According to Denis Dutton, a philosopher and the author of The Art Instinct: Beauty, Pleasure, and Human Evolution, this is because of evolution and the Pleistocene era. Dutton says that this typical landscape scene includes hills, water, trees (that are good for hiding in if a predator comes by), birds and animals, and a path moving through the scene. This is an ideal landscape for humans (protection, water, food).

https://www.blog.theteamw.com/2011/03/05/100-things-you-should-know-about-people-71-people-like-pastoral-scenes-2/