Probabilities matter. Cost-benefit matters. You can't just dismiss it with "well, some people don't commit crimes, therefore it's immoral to restrict freedoms." It's a gradient, and the people on the whole reserve the right to determine where the hard line is. This is one of the beautiful things about the fact the US has many states--each state gets to decide where they draw that hard line. If you don't like it you can find another state that draws the line elsewhere.