There is a race in the downswing between the left hand and the clubhead to get to the ball first. The left hand ALWAYS has to win that race.
For any shot hit off the ground, the golden rule is hit the ball first, the ground second. Getting the left hand to the ball before the clubhead gets there is the surest way for that to happen.
What most recreational golfers do is the opposite. The clubhead gets to the ball first because they hit with their right hand. More often than not the clubhead is coming upward, which frequently leads to hitting the ground first.
In addition, the right hand is flipping the club through the ball, taking the clubface out of line. The result is shots hit fat, off line, or both.
Those rockets you hit occasionally come when, by accident, the left hand does get there first.
Watch this video on how to learn this move, and practice what it tells you. I feel this move is the biggest difference between a consistently good ball-striker and everyone else.