Every few weeks or so, I catch a seasoned athlete not using hook grip on a snatch or clean. They'll be pulling early, or throwing their hips into the bar, or jumping forward, or missing the bar forward. Any of those faults are sometimes corrected just by adding the hook grip. Sometimes they even PR after using the correct grip. The athlete is amazed, and promises to always use hook grip forever and ever.
At CrossFit Fargo, we teach new athletes the hook grip in week 1 of Virtuosity (or beginner program). It's THAT important for good lifts!