I too live in Metro Atlanta and these upstairs lofts/bonus areas have been common for a very long time.
I have read nothing into it, except that it could be used as a playroom or a secondary sitting area/common area/study. I have been in plenty of homes that have these common areas that still have five bedrooms, so I really do not feel like they are replacing bedrooms with these areas.
I have walked through new construction, as recently as this weekend, where the homes have these rooms upstairs. However, some are more inclosed than others. I do not mean with a door, but more tucked away upstairs as opposed to at the very top of the stairs. I agree that the rooms at the top of the stairs may have limited use in that if someone had a TV on it would probably disrupt whatever is going on on the main floor.