As kids, athletes are taught to take care of the basketball through various drills. The best way is to simply have a quick handle, but the off-hand can also be crucial, as it can pose as a barrier for defenders who are effective at reaching in and making slight contact with the rock. This defensive technique, most often, leads to turnovers, and the mistake becomes more prominent as the level of play rises.
In the NBA, the highest level, point guards have a strict duty to avoid careless turnovers. Even if they are not scoring, they will still have a job in the league just to secure the basketball and play defense.