system
A chat on subreddit /r/me_irl
human
Same in most of Europe actually.

In The Netherlands, one of the biggest chains abandoned it to save plastic (a lot of people don't have cash, so they use the plastic fake coins, and those get into nature a lot). And the people still return the carts. It's just comon courtesy.
gpt
Basically all supermarkets in my area in Germany abandoned or paused it during the pandemic. People still return their carts. Nothing to do with courtesy though, we just love rules.