It’s mostly monolithic slabs and the occasional pier and beam. I’m not sure why stem wall slabs aren’t used here, but I’m sure there’s structural or geological reasons for it above my pay grade. I’d wager the lack of basements here is probably related to the same reasoning, whatever it is.
The soil is expansive so when wet, it expands and when dry it contracts. When it contracts, it leaves part of your slab unsupported so the slab sinks and your framing bends. When the soil gets wet, it expands against the foundation and applies pressure, supporting it. A lot of expand/contract cycles puts a lot of stress on the foundation and the rest of the structure. In my case, I’ll need to redo most of my indoor sheetrock, bathroom wall tiling, and a few door frames because I didn’t know I needed to water my foundation the first year I moved in, a few years past.