Earlier quoted context omitted.
That article is out of date. In large parts of central Stockholm, you can't pay by cash. Legal tender is just words, if they don't take cash there's not much you can do.
So how do poor people function in a cashless society?
Our major grocery store chains all still accept cash (ICA, Coop, Willys, Hemköp etc.) and at least ICA and Coop sells pretty much -everything- at their larger stores. They don't sell mattresses or furniture I guess, but you can go there with enough money and come out fully equipped to go camping for example. IKEA also accepts cash still, so you can buy your furniture there. Or even go get a nice meal there; a plate of meatballs and mashed potatoes costs 39 SEK (~3.7€, $4.1 USD). A BigMac&Co costs twice as much as a frame of reference.
I (a Swede) am able to use cash every single day, and it's not an effort to do so.