Outlawing Cash?

From the July 12, 2017 Wall Street Journal: “VISA has a new offer for small merchants: take thousands of dollars from the card giant to upgrade their payment technology. In return, the businesses must stop accepting cash.”

Last time I checked cash was “legal tender for all debts, public and private.” How can a business not take cash?

I have a VISA card, but I pay for most of my purchases in cash. Helps keep me from over spending, which would be fine with VISA. They want me to overspend.