Are you suggesting racers should loop their kites after each tack or jibe to untwist their lines ? Well no they prefer to ride with crossed lines (no big deal) as looping the kite on an upwind leg is counter productive.
When riding my surfboard one of my favourite moves is a double forward with kite loop . Untwisting my lines would need 3 consecutive down loops. A manual swivel is in my opinion more practical.
When rigging your kite a swivel allows you to attach the front lines to your kite without the need to untwist your lines (much faster).