True, but if they have the information your looking for, that's the first thing they are going to tell you. In fact it would require more thought and more bravery to lie.
It doesn't guarantee the accuracy of the information. People can say anything to avoid the pain. If you don't have time enough to check that information, it's better to dig in their thoughs
But of course if they don't know anything its just a waste of time, nonetheless my SI have never tortured anyone who doesn't have something he wants.
Torture also has other uses (don't I sound like a sadisitc evildoer) it can instil fear in your enemies, and loyalty in allies and vice versa. In fact normally its used to get someone to do something, rather than tell you something Which is much more effective than attempting to reason with them, or promise to give them something.