Amtrak service WASH - NYP - BOS almost sold out for Monday Jul 10th

Do not know if weather related or due to problems of last few days . Almost every train shows sold out or 90 % full. Now why can Amtrak not add some cars to those scheduled for tomorrow on the regionals?

Amtrak doesn’t have enough serviceable equipment to run trains at their pre-Covid capacity levels, let alone add equipment for peak usage periods.