To be honest, I always thought that was a bit of an anomaly. If you checked in online, at any point from 36 to 2 hours before departure, you got no choice of seat - just take what you are allocated by the system. However, if you went to the airport kiosk you got to choose from whatever was still available.
That said, once regular pax get wise to this, rather that paying extra for a chosen seat, I'd guess that more will go the check-in desk, where they'll be able to haggle with the agent, which must surely be the exact reverse of what the airline wants to achieve!!