I do return my shopping carts and I think this is mostly valid.
But with that said, I would say there is one key thing missing here and that is that the store must also make it reasonable to return your shopping cart. And most do! But if you have to walk 30+ seconds to put your cart back, in my opinion, they are just asking for people to leave carts everywhere. I certainly wouldn't expect pregnant women to return carts if the store doesn't provide appropriate infrastructure. Same for a single parent on a hot day that doesn't want to leave their kids alone. So is this mostly true, yes, but as a sweeping all-encompassing generalization? Probably not.