Because credit card fraud has had a few decades to evolve too, and is now orders of magnitudes more easy to coordinate. If word gets out that a given store has

Because credit card fraud has had a few decades to evolve too, and is now orders of magnitudes more easy to coordinate. If word gets out that a given store has no online processing and is accepting carbon slips again, you can bet that quite a few people with stashes of stolen/closed credit cards will show up and start buying the most expensive items in the store. The modern equivalent would be offline chip processing. That is actually capable of at least ensuring that a given card is not heavily overdrawn or outright forged. Still, even that is unfortunately being scaled back significantly, given that "everything is always online anyway, so why do we need it?"