Currently people with luggage turn up at check-in and have to wait in a (frequently long) queue to be processed before they get to the front of the queue, only to find that one of their bags is 1 kg overweight, while another bag in the party is 2 kg underweight. You end up with the passengers trying to frantically repack their bags to keep under the standard weight allowance, while everyone else behind them in the long queue grumbles.
Just booked with EZY for June and our two check in bags are a combined weight of 40kg, so it don't matter if one is over and one is under!