I've lived places where people conscientiously return shopping carts to the appropriate spot, diligently wheeling them back and tucking them in the stack. That's not how it works here.
Clearly the consensus is that shopping carts are an open-ended courtesy, and the public may do with them as they see fit. Responsibility for recovering them falls squarely on the store-owners. And not just from the far reaches of the parking lot. With a large car-less population, carts tend to stray far into the surrounding neighborhoods* where they are left and eventually picked up by the truck that patrols for them.
Many never make it home at all but are adopted for a new life in a variety of creative uses including but not limited to:
* With recent security improvements, this practice has slowed but not ceased.