There is a concern that if the screw loosens, the trigger stop can rotate far enough to keep the gun from shooting. I have never seen it to happen, but it is completely avoided just by leaving that little piece out.
The illustrated revolver has an aftermarket target rear sight, and if it is an IDPA SSR, would benefit from the trigger stop. I hate backlash in a trigger and would want one in a target pistol. Maybe not a duty gun.