In my opinion parallax is a non-issue when talking about big game hunting scopes. Under field conditions it's such a small part of the accuracy equation to be insignificant. Besides that if you position your eye in the same place behind the scope each time there is no parallax, regardless of the setting.
Now, in higher powered scopes used for precision shooting (long range varmints/target shooting) parallax can pose a problem. Hence, most scopes designed for this type of shooting have adjustable parallax settings.
And no there is no "automatic" parallax adjustment regardless of how good the optics are. They are either set for a given range or have a manual adjustment.