They would have had to. The industrial revolution was a killing blow. Moreover maintaining slaves was too expensive for most to continue. They had to be fed, clothed, get medical care. Much like blacks today want to be taken care of.
It was a benefit to turn those former black slaves into land owning sharecroppers. The plantation got the benefit of the labor without providing anything but a miniscule share value.
Adding insult to injury, poor whites also became share croppers giving the former slaves a bit of competition.