5. They want to swap.. I think a large percentage of people on this thread have reasons for choosing where they sit.
I had this debate with myself last night trying to decide if I wanted the exit row window (14A) or bulkhead aisle on a 738 (AA1070 RSW-DFW)
They were both showing middle seat vacant. I like being on the aisle, but I like how exit row prevents children and pets.
Do to out of control ESAs, most of which I believe are simply pets, I have decided I am going to prefer exit row.
Of course, on RSW-DFW, the flight filled, and both middles were used. I was in an otherwise empty exit row on the outbound Friday night.