It is the same Argument the Iranian and Afghan Goverments use to cripple the freedom of womans. AllahuMaga.

legal tender

As far as I understood it in the last 20 years, it is only legal tender for debt facing the goverment. No private business has to accept cash. They do not have to accept cards either. If they wish, they could demand payments only in acorns or bottle caps if they wanted to. Only govermental Institutes (eg. for taxes, fines, etc.) have to always accept cash so you can always free yourself from outstanding debits without needing a bank account as bank wiring or credit cards are a private 3rd party business that can not be guaranteed for every citizen (as banks can arbitrary decline service to people).