Why driveways drop here first
Driveways carry more weight than any other slab on the property, and they sit on ground that moves. St. Joseph is built on loess bluffs along the Missouri River. Loess is fine, wind-blown silt. It holds a shape well when dry and it loses volume when it gets wet or when water washes channels through it.
Add our freeze-thaw winters and the picture is clear. Water gets under the slab, freezes, expands, then thaws and leaves a bigger void behind. Each cycle takes a little more support away. In spring, the corner that used to be flat is now a step.