Most rotator cuff tears are the result of sports-related injuries. But there are other mechanisms of injury such as a fall (from a height or from a standing position), lifting heavy items, car accidents, or other accidents.
Is it possible that you have experienced one of these injuries in the past but just didn’t link it with the damage to your shoulder? If not, it is entirely possible to have an atraumatic (without trauma) cause of rotator cuff and labral tears.
Sometimes age related changes combined with imbalances in and around the shoulder and repetitive motions can lead to similar injuries. Most often, these apparent atraumatic tears are really related to a remote event several years ago. But because there weren’t any immediate symptoms, it’s easy to miss the connection.