Why are photos and videos always cropped on phone orientation?
The sensor in an iPhone camera is not square, it is rectangular physically. 

Therefore, ‘uncropped’ is rectangular and square is a crop of this. If you would like a square photo, you can use the square function in the camera app, but this will be a lower resolution as it is just a crop of the original rectangular image.



https://en.wikipedia.org/wiki/Image_sensor_format