We still use stone age money

Hartung is right, to an extent. The Federal Reserve study found that respondents of all ages used cash for 55% of transactions up to $9.99. But the larger the purchase, the less likely consumer was to use cash. A mere 8% of consumers used cash for purchases of more than $100.

Old things don't go away, they stick around where there is utility, the same with paper cash.

We still have stone age money, chiseled stone.  We see that in brass plaques on buildings, entrance boulders at national parks, Mt Rushmore, and steel land markers; all of that derived from stone money of thousands of years ago. The first use of money was  to establish territorial rights. The bigger the boulder you could move, the more certain your rights.