I suspect that the reason is: "I don't want to do that, and if I don't do it then somebody else eventually will, and if they don't eventually do it then that's their problem, and in any case I don't care."
Imagine a business that didn't periodically fetch their carts. The parking lot would be a hazard of loose carts, and the store would run out of carts for customers. So the store will have to do it anyway.
Returning a cart is a courtesy -- one where it is very visible (temporarily) when the courtesy has not been extended.
I think here the business would rather employ workers to yell at costumers, to return their carts, rather than start to collect them. Well, rather it does not need to employ them, they would do it own their own, but only until after the other costumers failed to yell at these people.
Imagine a business that didn't periodically fetch their carts. The parking lot would be a hazard of loose carts, and the store would run out of carts for customers. So the store will have to do it anyway.
Returning a cart is a courtesy -- one where it is very visible (temporarily) when the courtesy has not been extended.