I was cleaning out old gifs and had 3 showing their runner leaving early, like about 6 feet off the bag. Not sure why it is never called, but I can't believe it could be missed.
It is one thing if a slow mo or gif/video shows it and it is not called. Maybe it can be seen with the aid of technology, but not the eye. But... IMO if it is obvious in real time to the naked eye, then it reflects poorly on the level of the umpiring crew if they do not uphold the rules of the game.