The cash you make is reported to the IRS. The cash you save is reported to the IRS. The cash you invest is reported to the IRS. Large purchases, deposits, or withdraws made in or to cash are reported to the IRS.
Cash can be made and not reported, it can be saved and not reported, it can be invested and not reported. Hence it is true cash is king, even still today and it may just be to avoid the merchant card services charge.
I elect to spend numbers, symbolic of paper certificates, backed by nothing.
We are not to the point of trading precious metals yet.