...for the reasons you mention, but the THREAT of torture is probably extremely effective.

Another problem is that once you develop a torture infrastructure, even a "responsible" one with training, rules, procedures and so on, you're going to start attracting a lot of unsavory people, or people will be perverted by the atmosphere and the process and turn unsavory. And of course, there are always those who are neither authorized or expected to torture, but do it just because they think its fun, and they can get away with it.

I suspect, (well, at least, I hope), that a lot of this torture talk is just that, a means of terrifying potential captives into spilling the beans before they figure out nothing is going to happen to them. The most terrifying thing for a prisoner must be not knowing what will happen next, and thinking perhaps his captors are rogues whose superiors are uninformed of their activities and ignorant of their sadism.

The purpose of most post-capture detention is to make the captive feel abandoned, forgotten, vulnerable and disoriented. A sympathetic interrogator can exploit this and engage the captive in conversation which the prisoner will grasp at because of the humanity of his interviewer. Without asking specific questions the captive will be hesitant to answer, the questioner can still gather a great deal of collateral information of no obvious import which, when stitched together, reveal real intelligence. Good cop, bad cop.

Of course, the most high value targets will be trained in these techniques, and how to resist them. And although the captive always gets worn down eventually, he tries to give up as little as he can for as long as he can. Eventually, the interrogator has to escalate, time is always in short supply. Once your prisoner loses his fear altogether, you have to make him afraid again.

It's a nasty business, and I can't imagine anyone wanting to do it, but they always seem to find someone.