It was very difficult for slaves to run away from their masters. It seems like a easy suggestion for slaves to run away but it was really difficult for them to do. First they had to have a place to go to. The places up north that might protect runaway slaves was very far away. Since slaves did not have money, they had to rely on the kindness of others to help them escape. At one time slave masters would pay people to turn in runaway slaves.
So the slaves had to remember that. Another reason why slaves may not have run away is because their families were split up and they wanted to stay on the plantation in case their family members came back.