Because the fact of the matter is, as Teresa points out, that torture doesn't work. The axiom is "everybody breaks," and while it's not precisely true--see the subject header and google around the Salem witch trials for an example--it's true enough that the exceptions are statistically insignificant.
The problem arises because when you break, you don't tell them the truth. You tell them what they want to hear to make the pain go away, or to get a drink of water, or just to be allowed to sleep. And--here's the tricky part--in the process, you can in fact convince yourself that what you told them was the truth. Because you don't brainwash somebody else. That's not how it works.
You convince them to brainwash themselves.
And you don't need to go to a prison camp or a Virginia jail to see it in action. You can volunteer at your local domestic violence shelter, or you can talk to an adult survivor of child abuse.
It doesn't matter how strong you think you are. You will tell them what they want to hear, in the end.
So ask yourself--is this the government you want to live under? Are these the people you want to trust with your safety and your children's safety? Are you willing to gamble that they will not come for you?
I'm an adult survivor of child abuse, and I speak from experience when I say that you will tell them what they want to hear, whether you are innocent or guilty. It worked on me, and it will work on you too.