There are a few reasons why someone might have a gravelly voice. One reason could be that they smoke cigarettes. The nicotine and other chemicals in cigarettes can damage the vocal cords, leading to a raspy voice. Another reason could be excessive use of alcohol. Alcohol can also irritate and damage the vocal cords, causing them to swell and leading to a hoarse voice. Additionally, some people naturally have thicker vocal cords, which can make their voice sound gravelly even if they don't smoke or drink excessively.