You are combining two different issues. TSA's goal is to keep flying safe. If this can be done with managed inclusion, there should be more managed inclusion. You want the lines to be clear, which is a separate issue. Forcing more people through more intrusive screening isn't something that should be done in order for you to have faster moving lines. Perhaps it's time for there to be frequent flyer pre-check lines, like there are for the regular screening. That could both solve the issue of being stuck behind the person shocked to find out water is a liquid and metal detectors detect metal and having to pay for additional unnecessary screening. Face it: Not a single incident can be traced to allowing managed inclusion, so it doesn't appear to be an issue.