It's the most common reason online passport and visa applications get sent back, and the reasons are physical rather than a matter of effort:

Phone Cameras Distort Your Face

Held at arm's length, a phone lens exaggerates the features closest to it. Government facial-recognition checks compare proportions, and a selfie's proportions are wrong before you've done anything else.

Home Lighting Casts Shadows

Ceiling lights throw a shadow onto the wall behind you. Portals require a plain, even background with no shadow — which needs lighting placed to the side, not overhead.

The File Itself Usually Fails

Dimensions, head height as a proportion of the frame, file format and file-size limits are all checked automatically. A cropped phone photo passes all four by accident, rarely by design.