Sometimes they mess up and give points for flight booked but not flown, especially if checked in and the connecting flight is flown. I've even heard of points given for flights booked and then rearranged on the day of the flight to a later date. But it's cock-up and not intended, though why BA care if you fly or not, as long as they get their money, I don't know - is someone who pays for 10 flights and doesn't take them a better or worse customer than someone who books 10 flights and actually flies?