The differences reflect the nuances of the game. Ex:
Thrown ball INT is a higher bar because the defense 'controls' the throw and should be able to avoid hitting a runner (under normal circumstances).
A batted ball is NOT controlled by the defense, so they get near 100% freedom to react to and field the ball. INT standard is much less restrictive.
You just can't fully discuss every angle of history, intent, reason, problem etc of the rules on a forum...you could type for the next fifty years. This is better discussed in a bar over some pitchers of Yeungling
