The issue for Boeing is they are doing all the Tra-La-La about the 787 being the "most comfortable ever" when they full know that it is replacing, commonly, the 767, which apart from charter operators always had a 2-3-2 7-across layout, with the 787 being 3-3-3 in a 9-across layout in a cabin just inches wider than the 767.
It is quite true that airlines, not the airframe manufacturer, determine what the seating density is. It is therefore somewhat ingenuous of the manufacturer to do extensive publicity of their own (which Boeing have done) about it being "more comfortable" when they know full well that what their customers have done with it leads to it not being so.