I think that say something about how the city is designed.
I don't know anything about Atlanta but in Arizona, per parent comment's story, for example, it's strange to see people walking around because it's way too hot in 80% of the state to walk around for leisure. On top of that, the towns are so spread out that it makes no sense to walk from point A to point B.
So if people are walking around, they're doing so aimlessly in a climate that is not really conducive to doing so. It seems reasonable to think they're either in trouble or up to trouble.
I don't think it has anything to do with the temperature.
You see tons of people walking around in cities in equally hot or hotter climates, from Cairo to the tropics...
ORIGINAL: You're overlooking a lot of important factors.
Distance: I highly doubt people in Cairo are walking 10+ miles to the nearest market.
Attire: If walking around in the summer in Arizona raises suspicion, I cringe to imagine what suspicions would be raised by doing so in long flowing robes that cover skin head to toe.
Sweat: In my experience in the tropics, being a bit sweaty is quite normal and acceptable. In The South (the southeast) it seems more acceptable, but in the dry Arizona desert, it's not quite normal to be drenched in sweat.
Air conditioning: AC is everywhere in Arizona. As such, the mode of survival is getting from AC to AC as quickly as possible. If AC weren't everywhere, people would probably find sweat more acceptable, but... it is.
Skin tone: I'm pasty white and was born and raised in Arizona. In my travels to the tropics I never once ran into a person as white as me who enjoyed walking in the heat.
All of these together make walking pretty rare. Sure, if people didn't have another option besides walking you'd have a population of fit, well-tanned Arizonians all over the streets. Markets would probably be built closer to homes and suburbs would shrink. People wouldn't need cars and would probably be more comfortable without AC 24/7. As a result, a bit of sweatiness would come to be expected and wouldn't be a source of self-awareness. But that's not the reality of that region.
Most people drive cars, and most people prefer having some room to breathe, and there's no shortage of space, so lots are made big enough to have parking and empty space, etc.
There's not some kind of anti-walking design conspiracy here.
- Primary metric for road design and evaluation being "level of service", which means "how many cars can move through here in a given period of time". Pedestrians are second-class citizens.
- Minimum parking requirements subsidize car use and make urban environments pedestrian-unfriendly by spreading out points of interest.
- Zoning regulations mandating that most of a city's residential area consist of detached single-family homes on large lots, mixed-use generally limited or non-existent.
- Under-investment in transit (transit use is generally paired with walking at the start and end).
- Freeways running all the way into and through cities split urban areas into sections that are difficult to navigate between by walking.
I could go on and on about how American cities are hostile to walking, but that covers some of the big ones. It's true that these decisions have or had popular support, so it's not a conspiracy, but it was certainly designed.