You have no way to check if the people you torture told you the truth until it's too late. And they know it. So they will just lie, you will torture them some

You have no way to check if the people you torture told you the truth until it's too late. And they know it. So they will just lie, you will torture them some more until you persuade yourself they told you the truth, and the attack will happen somewhere else than where they told you anyway. But hey - you get to torture them some more after the fact to feel better.