Because most people believe torture works. They believe we shouldn't do it because it's "bad", rather then the reality which is that it's ineffective at information extraction.
Same problem with WMDs: people tend to think there's just tons of chemical and biological weapons which would definitely immediately win wars, and we don't use them because for some reason dying by a bullet is "better" then dying nearly instantly from nerve gas - like that makes a difference.
The reality, again, is that they don't actually work (specifically: they are ineffective against military forces in achieving military objectives, but very effective against civilians who are unlikely to have counter-measures on hand and/or too uncontrollable to be create a useful strategic advantage).
EDIT: Like to drive the point home, in Zero Dark Thirty - which the CIA got to consult on - the line is that a prisoner broke under enhanced interrogation...and while it's true Bin Laden was located by intelligence from a prisoner who was tortured...they didn't get the intelligence from the torture. All the information which was useful was found by regular interrogation before they tortured them.
Same problem with WMDs: people tend to think there's just tons of chemical and biological weapons which would definitely immediately win wars, and we don't use them because for some reason dying by a bullet is "better" then dying nearly instantly from nerve gas - like that makes a difference.
The reality, again, is that they don't actually work (specifically: they are ineffective against military forces in achieving military objectives, but very effective against civilians who are unlikely to have counter-measures on hand and/or too uncontrollable to be create a useful strategic advantage).
EDIT: Like to drive the point home, in Zero Dark Thirty - which the CIA got to consult on - the line is that a prisoner broke under enhanced interrogation...and while it's true Bin Laden was located by intelligence from a prisoner who was tortured...they didn't get the intelligence from the torture. All the information which was useful was found by regular interrogation before they tortured them.