When someone gets into an accident, it is required by law to stop and is most cases they often call the police to report it . However this is not always the case because many accidents are minor and people would rather move on for a variety of reasons. IE Not wanting to get insurance involved or in a hurry and do not have time to do an accident report. In other cases a driver will not want to stop at the scene because they are undocumented or may have alcohol in their system and do not want to put up with being arrested.