My faucet has a high-arc spout, and it does not immediately shut off after the handle (or handles) are turned off. Why is this?

This is a normal characteristic of any faucet with a high-arc spout. After the handle (or handles) are shut off, there is still water inside of the spout. Any residual water past the arc of the spout will slowly drip out of the spout. Gravity will pull this water from the spout; however, it should stop after several minutes.