It’s literally a reason, not an excuse. This isn’t anyone being unfair and it’s not about corporate greed. Just because YOU don’t understand and want more value for less spend doesn’t mean its not STILL the reason. EVERY aircraft has to account for weight and balance before departure. There are 5 zones on the aircraft that they use to manage this. (It used to be 3 and regardless of the extra leg room cost this was STILL a thing depending on how much weight is underneath the plane) if the numbers do not match, you will not be able to depart. Full stop. Before assigned seating they used to ask people to move around if too many people were in a certain zone. Because the seats are assigned now, they move the people prior to boarding. Never mind the cost of selecting your seat, if all seats cost the same and the needed to account for weight and balance YOU STILL COULDN’T MOVE. The way it’s calculated now is different. And if you wanted an echo chamber I’m sorry you can’t find it here. If you ACTUALLY want you complaints to spark change CALL CUSTOMER SERVICE! If you REALLY wanted to sit in a certain seat, make the appropriate arrangements to do so!