If you serve and I think it is in I will return the ball. Your job is to play my return until I have told you it was out. You are not disadvantaged if I play an out ball ... unless you stop playing yourself.
If you were allowed to call first serves out then you would be in the position to see my returns and then decide to call the ball out. This would put me at a clear disadvantage if every good return I made was met with a late out call from the server.
It seems to me that however the rule was written a nefarious person could take advantage of the rule ... The USTA, ITF, and every other organization has decided the player on the ball side of the court should have the responsibility as to whether the ball in is or out. They have been very consistent in this regard.
"You should be playing linebacker, not singles."