Texture helps to hide hairline cracks and imperfections in the drywall, which would normally show through to the finished paint. It also helps to add character and depth to the walls and ceilings.
Ceilings tend to be the most exposed part of a drywall job. Light thrown across it by ceiling fixtures really bring out any irregularities in the surface. Walls are usually broken up by furniture, windows, door or wall hangings, so their flaws are a lot less noticeable.
The most common way to treat a ceiling is with a texture to help hide any imperfections. One treatment we’ve used is sometimes referred to as “Santa Fe Skip.”