I've heard tortue has inconsistent results. It will work fine for some people, but won't have much of an effect on others.

It might be more simple. If torture doesn't work, you're back to where you were before. If prison doesn't work, at least they're off the streets for a while.

I don't see why imprisonment is considered less horrifying than torture. It doesn't suck nearly as bad per unit of time, but it lasts longer. It's just a less dense version of torture.