For me it depends on the store. A normal grocery store: I will always return the cart. A luxury store: I don't, I consider it part of the service that I'm paying more for.

A real luxury store will push your cart out to your car for you and then bring it back.

I have one store near me that does that - we buy most of our groceries there because they are close and cheap (Aldi is cheaper, but everyone else is more expensive)

What the hell is a luxury store? Can you name any brands? I don't think we have them.

The ones I'm talking about don't have brands; they are local boutique groceries.