Then why did the majority of legally freed slaves remain in the south to live? And if the north was so great, why did the state of Illinois auction off black people into indentured servitude for the "crime" of simply crossing into their borders and staying too long?
Those questions are of interest but are not an adequate response to the well known FACT that fugative slaves were one of the Slavers' greatest problems. In addition, in the state of Virginia freed slaves were NOT ALLOWED to stay there by state law. Besides comparing a free man's actions to those of a slave is silly.
Why did so many Jews stay in Germany after 1933? The world is full of people who live under tyrannical systems that oppress them but they don't leave and the pull of home and the hope that things will get better is a powerful thing. Some of them don't know where they'd go. Some feel the devil they know is better than the devil they don't. Some don't want to leave family and friends to live among strangers. Some can't afford to move. There are lots of reasons. After a couple of generations, though, blacks did leave the south in great numbers in the Great Migration.