Isn't that illegal?

Only illegal to not accept cash for debts. A merchant can refuse to do business with you in cash since you're not in debt at the checkout counter (as no transaction has occured)

Ah, I thought it was the claim about "legal tender". As in, my folded-up $10 bill is legal tender, and you (the vendor) must accept it, even if you don't like dealing with cash registers, coins, petty theft, and counting change.

It's illegal in San Francisco

hmmm, wonder if it's a preventing cash theft sort of thing with cashiers or something in that space.

It's a few things, most likely. It removes human error (did you give the cashier a $1 or $100 bill?), reduces risk of loss/theft of physical assets, reduces staffing costs (One person can operate one manual till, one person can operate 15? automated tills where they're basically just overriding weights and checking ID for alcohol), is probably _cheaper_ than handling cash (because you already have a visa/mastercard/payment provider contract who will give you discounts for increased volume, and they likely charge less because of the topic of this article).

The interesting thing is, both of these store chains already had fully automated checkouts, they simply removed the ability for these to accept cash and make change.

The recent proliferation of "digideals" which require that you scan item barcodes with your handheld also is also popular. These deals are usually very good, often half-price. But w/o a cellphone you're locked out of the deal.

There will have to be at least one store that takes cash, though, or the people who don't have cards or phones will starve.