The point is that there's a serious opportunity cost. By prioritizing customer service (to some degree), airlines can't charge sell space to businesses moving c

The point is that there's a serious opportunity cost. By prioritizing customer service (to some degree), airlines can't charge sell space to businesses moving cargo for a higher margin. The coffee shop argument doesn't really work because you can't keep scaling it. At a certain point people want space for books. But given that there's a space shortage on international flights, there's probably room for airlines to make more money by charging for freight instead of taking your luggage.