In my opinion in out stations it's complicated by the fact that check in counters are not owned by the airlines but pay for them on a hourly rate in some cases. The same with the staff. It's easier for the handling staff to check in all the passengers and baggage and close the flight and vacate the counters or reduce the number of counters open if they have a huge delay.
But I agree with you in that if they inform you then they should respect and expect passengers would come in time for the check in for the new departure time.