That would be a LOT of magin they would be unnecessarily giving away. In the last round with the 12, a large part of the mergin per unit was the upgrade from base storage to the next higher storage amount. The market would take them down 3-5% if they did that, which is oh about 100 Billion in market cap.Apple should have never put people into this position in the first place, by not making 256 GB as the base storage for the Pro models.
Sure, it would be great for the consumer, but really bad for increasing or maintaining margins and the company would suffer. As well, I doubt they could justify it with much increase in overall sales since most android companies already GIVE higher storage and I doubt that is the real differentiator from a consumer purchase decision.