But not sure about why they're skipping the cash? Isn't the whole point of money that you can sell your item A to someone (who doesn't have what you need but wants A), then hand the money to someone else who doesn't want A but has item B that you wanted? Thus removing the need to match trading partners who both have what the other wants.

Why drop that advantage? If it's about complexity of electronic payment systems, taxes, .gov tracking or whatever, just stick to physical cash. Or a local coin. Or lumps of gold, ...