Oh, another reason: using payment cards means that every transaction is linked to your identity. If the state doesn't like you, it's very hard for them to stop you from buying a hot dog from a street vendor for $5 in cash. It's very easy for them to point-and-click stop you from transacting (without due process) if everything is card payment only. With the way most people buy mobile service (identity-payment-card-linked), this makes it possible to e.g. deny transactions (including purchase of food) to everyone that was in a certain street protest.
The ways they have of making your life inconvenient escalate to making your life completely unlivable (e.g. unable to buy food/clothing/shelter, or ride a bus) in the absence of anonymous payment systems.
BSA/PATRIOT make it illegal to issue payment cards in the US that aren't strong identity-linked.
Cash isn't so much useful because it's cash, it's useful because it's not linked to identity. If anyone could buy prepaid payment cards that didn't require identity, then this would be much less of an issue (but would still link multiple transactions together in time and space, which is its own privacy issue).
The ways they have of making your life inconvenient escalate to making your life completely unlivable (e.g. unable to buy food/clothing/shelter, or ride a bus) in the absence of anonymous payment systems.
BSA/PATRIOT make it illegal to issue payment cards in the US that aren't strong identity-linked.
Cash isn't so much useful because it's cash, it's useful because it's not linked to identity. If anyone could buy prepaid payment cards that didn't require identity, then this would be much less of an issue (but would still link multiple transactions together in time and space, which is its own privacy issue).