Contracting your wrists nets you quite the advantage and can often cause wrist dismemberments in an aikido match, which is not optimal.
Also the elbow control that comes with the inside grab (when you can dq their elbow by using force from your wrist) is a bit of a problem.
When both players do not contract their wrists, both players have the same advantage and both rely on their skill to win.
It also looks better but that's just my opinion.