The temptation is to always shoot a landscape image in the orientation named after the genre, landscape. After all, it must work right? But to do so would mean limiting the possible compositions without any good reasons. In fact many years ago I heard this expression which has stayed with me ever since, "When is the best time to shoot a portrait version of a landscape, after capturing the same image in landscape"
Landscape images that are composed in the landscape orientation, because the eye predominately moves in the x axis along long horizontal lines, feel very calm and peaceful. Sure if there is lots of detail in the scene then this can be reduced, but in general this is true. Images with lots of long vertical lines ( and landscape captured in the portrait orientation have these) have a more active feel to them, they create a sense of depth and motion. If you haven't tried capturing a landscape image in portrait orientation, give it a go, it can be quite an eye opener.
Here is a shot from Ohawe beach similar to the earlier one, but captured in the portrait mode. I like the way the rocks lead the eye to the cliff, only to return by the second line of rocks. These strong implied lines form an important aspect of the composition. I also like the counter balance of the light and cliffs at the top of the frame with the detail in the foreground. All of these elements give a sense of motion and energy which I like. That's part of letting the scene choose the composition rather than always preferring to shoot in the same orientation.
So why do you think the landscape orientation is so popular?