When I did the gate agent for a day exercise at the DL ATL DO, *my* GA seemed to make a standard practice of moving seats to enable those traveling together to sit together.

To me, it would make sense to move people so as to give elites empty seats next to them if the flight isn't full.

I wonder whether the seat moves in the OP's case are due to the selection of space normally blocked to be used by the GA for the purpose of seating families together. Maybe GAs are changing the OP's seat in anticipation of needing seats together. Alternatively, they might be assuming that the OP didn't really want to be among families with kids (especially when traveling alone on a B fare, so presumably a business traveler) or in the last row next to the lavatories or noise from the rear galley, but picked the seat because it was the only aisle that was left when the ticket was purchased.