You have to ask yourself why people have lost the innocent-until-proven-guilty concept. We still teach it in school, so it's not lack of exposure. Is it the media? Since 9/11, the number of police procedurals on TV have skyrocketed. Social Media? Journalism? Personally, I'd be very interested to see how well these concepts are distributed among class, race and gender lines.
In 1993 the Gallup poll found that 64% of the public agreed with the following: "Regardless of what the law says, a defendant in a criminal trial should be required to prove his or her innocence." In the same poll, 70% of the respondents agreed that our judicial system makes it too hard to convict people accused of crimes.
I would argue they dont actually. While they may say the words they ring hollow in the face of other lessons in schools, lesson around the hero worship of police, and government in general
Students are at the same time told about "innocent until proven guilty" while at the same time filled with all kinds of propaganda about how wonderful and infallible the government is.