I'm a little puzzled as to what the fuss is all about - to me it seems like an improvement to the airport
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.
If a few sets of baggage scales are provided in the check-in area (for a small fee - the airport is a business which wants to make a profit and these machines are not cheap), it means that there should be less repacking at a desk, the check-in agents don't spend ages waiting for passengers to figure out what to move between bags, and the people in the rest of the queue don't have to wait
I would imagine that the revenue from the scales should easily cover the cost of calibrating them once per week
Most LCC passengers know that if their bags are overweight, they will be charged heavily. Giving passengers a chance to weigh their bags *before* they get to the head of the queue in order to reduce a much larger airline charge seems to be a way of making check-in more efficient, reducing the waiting time of the other passengers and the check-in agents, and making the repacking process a little less frantic / stressful.