Comment by thaumasiotes

In the United States, carts are free. There is a stereotype that homeless people have shopping carts in which they keep their things.

There's no particular need to change this, because one person can only use so many shopping carts. If you maintain the price at "free", demand saturates and people stop stealing carts.

It's common for people to return carts to a designated area, and it's also not rare for people to just leave the carts somewhere convenient for them. Store employees periodically go around and move the carts back to the place where you expect to pick them up.

Costco is an interesting hybrid case. They make it easy to return the carts "correctly" by providing little depots scattered throughout their enormous parking lot. Realistically, the parking lot is so large that very few people would be willing to return a cart to the front of the store, where you get the cart from if you're going shopping.

However, people also aren't going to pick up carts from those depots deep within the parking lot and wheel them over to the store. So Costco employees still have to make rounds of the parking lot and move carts that have been left there to their correct location at the front of the store. But for Costco, you're supposed to leave the cart in the parking lot, but only in certain locations.