I think it was more of a psychological torture - since Hurin would not yield under personal threats and physical pain, Morgoth, the clever sod that he was, decided to take a more sinister path. Torture Hurin's children and make him watch, helpless.
Also, remember the children of Feanor - they had a sworn oath to fight against Morgoth because of their father and, mostly, followed it to the best of their ability. When someone takes and tortures your family, it must be hard not to harbour ill will towards that person. So, while Morgoth held Hurin, there was always the risk that Turin might raise armies to fight and thwart him, all in the attempt to free his father.
It is, perhaps, a testament to the weakening of Morgoth's power that Turin is, in many ways, successful in his attempts to thwart him, despite the curse. He kills Glaurung, after all, though with perilous consequences - and he does raise a number of armies against Morgoth.
So, yes, Morgoth is a bit of a sick fellow. Torturing Hurin by cursing his family. All in the hopes of getting a bit of information.
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