My thought is that, although much of this is common sense, retailers have largely lost the will to live. They waste a lot of money on typical corporate money pits, but tend not to try improving the retail business itself. From what I gather in what people say, having only been to one Aldi before (so I don't really have enough experience to say much); I think Aldi has bucked the trend, and is trying to do a good job, and that is why they are succeeding.

> depositing a quarter for a cart eliminates the need to pay people to collect carts

I've seen Americans remark specifically about shopping cart deposits a couple of times on Hacker News; I never thought there was anything special about it.

I think the vast majority of retailers and grocers who offer shopping carts, in the three Canadian provinces I've lived in, use coin deposits for shopping carts.

They still end up in rivers and alleyways on occasion, usually stolen by vagrants and hooligans, but the customers at least tend to comply.