There was no way to move 4 pounds of stuff into any other bag, even a carry-on bag of some sort? It seems a bit odd to argue it for 30 minutes instead of try and reduce it down to 70# and move stuff into another bag of some sort.

The punitive nature of luggage over 70# is to heavily discourage people from doing so. Luggage is still handled by people along the way (moving from luggage belts in the airport to carts, from carts to the plane, and then vice versa when offloading.) Heavy bags may either require two people to handle whenever moving it, or at least be something that one person can't do regularly. Two 49# bags (since the standard weight limit is 50#, though some tickets allow 70#) are likely much easier to handle from that perspective than one 74# bag.