Why is theft from a store stealing and not withholding payment? It would be one thing if I stole money from the cash register, but if I took an item the store

Why is theft from a store stealing and not withholding payment? It would be one thing if I stole money from the cash register, but if I took an item the store had for sale, the store consented for people to take items out of the store in exchange for payment, I did what the store consented to do, I just hadn’t completed my part. Point is, I’m not arguing with your legal argument but from a moral perspective, the law seems (in)conveniently bent towards supporting institutions and not people. If Amazon kept your money and didn’t deliver a product, then yes, they should be held criminally responsible.