What's the Point of TSA PreCheck if You Still Have to Get to the Airport 2 Hours Before Flight Departs?

Seriously. I am trying to plana day trip to NY from Chicago and was hoping TSA precheck would allow me to arrive 1 hour before my flight departs instead of 2, saving time. But I looked it up and they still recommend arriving 2 hours early. What gives? What's the point other than to not have to stand in the security line?