The article and the topic had me baffled for a while. I have never lived in any culture with a 'bar tab' culture and I've lived in twelve different cultures. It wouldn't work most places.
In my native Britain, it is very rare and only an honour bestowed on very regular customers who are drunks with money. The whole British 'buying your round' culture depends on paying as you go.
One exception I can the think of was in one somewhat seedy bar in the basement of a Soviet Moscow hotel opposite my apartment in the 1980s, but that was only because the bartender was terminally lazy and wouldn't even take your order. He just plonked a bottle of vodka, a bottle of Georgian brandy and a bottle of Russian 'champagne' in front of you, handed you a glass and let you get on with making your own коктейль, a cocktail made my mixing the three to your own formula. Lethal stuff. Any payment (if you remembered to pay) was on a trust system.
Paying with your phone is quicker than using a card or cash.
I also have problems with all this generational stereotyping. It makes as much sense as astrology.