It was solved for a brief time. Now people have these plastic coins you sometimes recieve as a promotional gift and since it is not a real coin, people stop putting the carts to the corral. You can witness this every time holidays are coming up and people are stocking their groceries. And the culprit is always middle-aged Karens who also don’t indicate when leaving the parking lot in their SUV.
This is a 1972 documentary about the life in the year 2000. It is in German, but English subtitles can be set up in the video settings. It turned out to be a bit different, but some predictions back then came to reality.