It's an interesting point. Stanton is an unusual case because he was signed to a huge contract as an outfielder, but he became almost a full-time DH due to nagging injuries. A player like this would probably be a first baseman if there was no DH, but the Yankees may never have traded for him after his 2017 MVP season if he played first base.
There are only so many starting jobs as first basemen to go around!