People like landscapes. Since the first cave dwellers looked out of the first cave mouths at the vistas surrounding them, and felt that familiar connection to the world its seasons, its emotions, the peace of natural spaces humanity has found an affinity with framed views of the world outside its windows. That affinity has remained undiminished through the ages, with representational (and, latterly, even non-representational) art paying homage to the depth of feeling all people experience in conjunction with views of their planet's outside places. Landscape painting, from the trompe l'oeil frescoes of 15th century Italian villas to the awe-inspiring openness of a simple Rothko, speaks to the heart of man in ways that no other images can.
Landscape painting captures more than trees, horizons, seas and mountains. Landscape painting distils the feelings these views engender. With a mountain range or open desert framed and placed on a wall, people can carry those feelings into their homes. The serenity of a Scottish dawn, or the violence of a heaving sea, carries the observer in moments of reflection to the plane of emotion with which it is associated: awe, wonder, beauty.
For Westerners, whose increasing modernisation has removed them physically from the natural world that produces these images, landscape painting is a vital way of staying in touch with the power and grandeur of the earth. The four walls of a flat or house distinctly keep out the views that remind the soul of its connection with the wider world: landscape painting is the only way those views can be reinstated. And without the views, the "older" soul the common racial soul of all humanity dies.
That's probably why landscape painting has traditionally been so popular in Western art, or the art of "civilised" peoples. Representational landscape painting doesn't occur in the art of tribespeople, or most Eastern societies the one notable exception being Japan, whose fusion of nature and civilisation made it famous for centuries before upstart Western societies got in on the act. Aside from the rule-proving exception of the Japanese, who never really removed themselves from nature: landscape painting occurs en masse in cultures where the business of living has left the natural world behind.
Small wonder, then, that landscape painting has always been such a popular choice for decorating Western homes. There's nothing more unnatural than a brick box whose sides are mostly designed to keep the world out landscape painting became the Western way of letting that world back in. Nothing brings serenity to the soul like a favoured vista and nothing brings that vista into the home like landscape painting.