Can't compare hospitals and corporate office buildings to rentals. Commercial space has extensive building systems that run horizontally with each floor (12' slab to slab and 9' ceiling heights leaving 3' to fit these crazy building systems/wiring in each floor). All rentals need are an efficient layout that allows vertical piping to run up and down through unit walls (aka floorplan "stacks" where bathrooms/kitchens are located in the same spot up and down the building). Construction is totally different. Residential is about 10' slab to slab with 9-9.5' ceiling heights, so just one of the many differences.
Building systems such as mechanical rooms, elevator lifts, air handlers, chillers, pumps, etc are required for even small commercial buildings, and they go up top. Heavy stuff that can't be supported on wood framing. Most of these garden apartments on the SS simply need flooring that will support a bed and the HVACs are the same kinds of units you'll find at houses, and they are located on the ground (on the roofs or even individual balconies in value-engineered mid/highrises...but they are light). Usually garden apartments don't have elevators...but the ones that do are interesting to see UC as you'll first see a bunch of 4-5 floor stone shafts, and then you'll see the wooden structures built around them.
Here's what I can tell you...we've had shitty stick construction in FL for decades now and very few fires to show for it...and surprisingly the construction has held up in hurricanes, too. Doesn't mean there haven't been mold issues, however!
Also, besides code, land prices, job centers, demographic trends, etc. in most Sunbelt cities people (even 20 year olds) are used to having so much for so little (in terms of material goods). This means renter preferences are for interior finishes, space, and amenities. Cities in the south are desirable because they can give a person these things for less, but the cities themselves usually don't have much more to offer. Developers must build units that can be rented out at prices not too high for the area, and with the many features desired in these lower income lower COL areas.
In SF all people want is to be able to afford to live in the city...so you get some dumpy shoebox studio for $2 or $3000, but you're never there and you're in the city enjoying what it has to offer. In Jax, you get paid less so there's no way you can afford too much more than $1000, and the city doesn't offer you much so the apartment damn well better (plus whereas in the big cities young people meet each other out and about more, in less developed cities like Jax, young people either know each other from growing up or they meet in the free gym in the building).
Developers can't build some high quality thing and include granite counters and abundant amenities and free parking, etc and rent them for what the market can afford...so you get shitty construction and bad architecture/design in low density suburban areas, but you get your top priority "must-haves" apartment features.