I have to agree with you OP, I have no clue what the point of paid seating is. I've paid twice for seating with my partner and baby. Both times we have been moved from the front to the rear at check-in. I wasn't best pleased. Got a refund and cursed myself. BA is going down in my book although this could just be how it is to travel with a baby. Being placed at the rear, board last, have issues with the baby bag, and then staff trying to help by taking it away from us to the other end of the plane. Not ideal.