It isn't their fault. When the mucous membranes become stuffy and swollen, the air passages become smaller. You then have to breathe with exaggerated force to move the air through the narrow hole. This explains why some people only snore during hayfever season, or when they have a cold. Anatomical deformities in the airway.
Some people have a broken or crooked nose, which cuts down on the airway size.
Being overweight can also cause snoring, because fat deposits around the upper airway make the airway smaller. About half of all adults snore occasionally, and one out of four snores regularly. Snoring is much more prevalent in men than in women until menopause, when almost as many women as men snore. Children may snore if they have enlarged tonsils or adenoids. Treatment is necessary only when snoring is a feature of Sleep Apnoea.