It's not just people happy to talk. the interrogators are trained to catch certain signs that the interviewee is telling the truth. But if the cops miss those signs or choose to ignore them, the interrogation can go on for hours and hours, plenty long enough for people to be "brainwashed" into remembering crimes they never committed in great detail. It's kinda scary how far they can take someone with stress, sleep deprivation and hunger, in only a relatively few hours.
Later Reid courses actually show a tape of an interrogation where someone rewrote their own memories.