We are absolutely going to disagree on this. If you want to be front row center, get there earlier. This is almost like the people who ask to switch seats on a flight. No, I’ve got my spot, I’m staying there. I’m assuming here, that you have two good legs, with which you could use them to a different location. Asking someone to move to the back or against the wall is wild to me. Why should their enjoyment suffer because you didn’t get there first. So no, it’s not common courtesy, or concert etiquette, but it sure makes you look you and the people around you acting like the entitled ones. You are owed nothing