98 miles of 45 foot deep water,  maximum,  and a narrow river,  requiring pilots for both the bar crossing and then the river voyage,  added to the cost.  Container ships a quarter of the size and smaller,  of the new ships,  which use the same amount of fuel and crew,  but carry only a quarter  as many containers as the new  generation container ships,  adds to the cost per container..  Maersk and the other mega shipping lines are mostly engaged in China to LongBeach-Los Angeles routes,  or soon,  the Panama Canal with it new upgrades able to handle larger vessels.  

SF-Oakland, also a terminus of transcontinental railroads as are Portland and Puget Sound,  has environmental resistance to even maintenance dredging of their port docks.  So,  ships have to move at the top of the tide,  even to move to another berth.  Any movement requires a tractor tug and pilots on board.  Dredging will become the issue that kills both Portland and SF/Oakland.