I don't think torture is used to punish someone. Putting for the sake of interrogation aside I just don't think there is much point, a lot of trouble, expense, time, energy and inventions just on trying to punish an undesirable? Why not just kill them? cheaper, easier.

The point of torture is not to punish someone, it's a forum of entertainment and curiosity for the torturers.

Just seems weird... and all these different techniques that people have come up with.... it seems a really bizarre practice to me.