On a flight with American Airlines from Orlando to Dallas in July, the crew came around and asked those passengers in the exit row if they would be willing to assist in the event of an emergency. They said that they wouldn't be willing and they were moved to different seats. A non-English speaking man then moved across to the now-vacant seats. He too was asked the same question, but he couldn't answer, so he too was moved!
Whilst this couple have been treated badly from a customer service point of view, I am sure that even they can understand that safety is a priority. In the event of an emergency, these pensioners would be relied upon to open doors and evacuate quickly, clearing the way for other passengers. I don't dispute that there are some very fit, healthy and active old people out there, but the majority are not what they once were. They might struggle with heavy doors and their inability to move quickly could delay the evacuation. In an emergency - a fire for example - the extra time could have catastrophic consequences for those stuck inside.
I do not fly with airlines that impose charges for silly things i.e. an 'extra legroom seat', which is actually an emergency exit row, but I am certain that, at the time of booking, a date of birth or an age would have been collected, whether by the airline or a travel agent. Knowing this, the airline should have contacted the passengers before they reached the check-in desk. They will certainly get their money back and I think they deserve some compensation, too.