Most people can’t draw what they see. When they use a pencil to transfer an object or a scene onto a sheet of paper, they tend to draw not what they see but what they know. Or at least what they think they know. So a sketch of a face ends up looking like a Cubist sculpture, and a drawing of a street scene looks like primitive folk art.
Optical, or naturalistic, perspective doesn’t come naturally. It requires a trick of the mind, in which you use your executive brain to override your beliefs. Instead of looking at a subject as a three-dimensional person, place, or thing, you mentally flatten it out to two dimensions, focusing only on the relative distances and relationships among lines, edges, angles, and shapes.