There is a strong tendency for smartphone users to take vertical photos and video. This is understandable. It’s more comfortable to hold the phone vertically for taking and viewing the shot. It’s the default orientation, but artistically, it’s often the wrong choice.
Back in the olden days before cellular phones, people used a portable device called a camera to take photos. The natural grip of a camera was in the horizontal position. The default horizontal design was not accidental. Given that we have two eyes, human vision has a wider horizontal field of view than vertical. Therefore, a horizontal photo better replicates what we see out of our eyes. Horizontal photos are a sound choice for many scenes, such as landscapes, a room, or a stage.
Verticals make sense when you want to emphasize the subject of the photo while minimizing the background. Verticals are often used for portraits. Also, there is a practical reason for the use of verticals. When producing social media video for TikTok, Instagram, and the like, vertical video is the expectation. This content is consumed on smartphones that are held vertically.
For those in the Apple ecosystem, you’ll be much happier if you have an appropriate mix of horizontal and vertical photos. I.e., the orientation should be an artistic decision, not one of convenience because it’s easier to hold the iPhone vertically. Unless you’re taking video for social media apps, always shoot video horizontally. Vertical video looks awful when playing it back on a Mac or TV. There are huge black bars to the sides of the video, and much of the screen’s resolution is wasted.