The debate free will vs. determinism is useful when trying to understand human behavior and the social world.
This debate has been very well known in sociology and in psychology, there are theoretical perspectives that are closer to one side or the other, theories that are closer to the free will perspective, state that human behavior is a product of our own choices, that we have the ability to choose; determinism states the opposite, that human behavior and a person's social conditions are determined either by genetics or by social conditions, there is no possibility for change.
It is a mistake to asume that we have full capacity to choose or that the social world is determined to be as it is and social change is not posible. I believe the debate is usefull because it helps us understand how society shapes our life conditions and which factors, like race and gender, determine certain life experiencies. But also, it is usefull to study social change throughtout history, to identify how social groups manage to change their life conditions.