After doing dispatch for years you found that if pax checked in on line and had a boarding card, they didn't need to go via check in but came direct to the gate. They could check in on line, not check a bag for the hold but bring one anyway and go straight to the gate in the hope they could carry it on.
Some were laughable, couldn't even lift the bag never mind put it in the sizer and the others who were regular travellers new that as they went through the gate and if challenged, the bag would be taken as a hold bag at last minute and due to proximity of departure there was no way they would be charged for it.
On line check in was a pain for dispatchers as you had an idea that they had a bag that wasn't checked in at the front.
Having said all that, I think that check in staff got commission on excess baggage taken at check in but not sure about normal hold bags.
Might just have been one of these off days for an overworked and vastly underpaid check in staff.
BMIBaby was the one that was highlighted last week or so.
Fly safe