> Imagine leaving your keyring on your cart... yikes!

While you're shopping? That's not a big deal.

When you return the cart? How are you driving home without your keys?

I guess Europeans might be more likely to not take a car to the grocery store, but I would prefer to use a basket over a cart while shopping in that case... I'll know when I'm done shopping when the basket hits my limit of how much to hand carry.