In lasso guard, it is important for the guard player to control the sleeve at the wrist in a manner that doesn’t allow their opponent to circle their hand out of the lasso.
Keeping this grip anchored to your own hip while simulaneously pulling and applying pressure with the lasso’d leg pulls all the slack out of the opponent’s arm, making it easier to maintain.
Being loose and sloppy with grips will likely result in losing the lasso and open you up for over/under and stack passing.