eCommerce is inherently cashless by design. Confined / captive environments (e.g. airplane cabins) are cashless. Concessions and merchandise counters at large events (sporting events, concerts, etc.) are cashless. Self-service kiosks for anything (or vending machines) are increasingly cashless. And if memory serves me correctly, I believe that using cash to purchase real estate via arms-length transaction is prohibited in the USA by law, even if the buyer and seller agree on the use of cash (and if it was logistically feasible to do so).

I would argue that cash is not an option in more cases than it is an option.