In some regions, instead of slab-on-grade, the minimum height of the main floor above grade can be 36"/915mm. If the area floods, this allows water to pass under the house.
Before flooding requirements dictated foundations, it was often for economic reasons crawl spaces were built instead of full basements. You’ll often see this in split level style American houses where the living room side is built over a crawl space and the first level up (often with bedrooms) has a full basement under. The actual slab under the whole house is then at the same level.
This arc is a great narrative on how self-centered people are and completely unaware of what’s going on around them. I’m sure we all see it everyday…!