In that movie the way that person specifically had been buried was a punishment. If I’m not mistaken they had said he had been buried alive as evidenced by the scratch marks on the inside of his sarcophagus. Mummification was not a punishment. The vast majority of the Egyptian population was not mummified as it required specialized persons to perform the rituals. It was performed on the wealthy and the pharaoh as well as his family to ensure an eternal afterlife. Hence why they were buried or entombed with everyday essentials, favourite items from their lives, even had favourite scenes depicted on the walls such as hunting. Statues (and sometimes actual) servants were included to provide companionship and personal help in the afterlife.

Most of the population was buried was they are today