> In what situation were you as a foreign traveler where you needed to pay UPI?
If you live in a tiny bubble and only take an Uber to the Work Campus, Uber to the small number of marts you've found that accept card, Uber to the small number of restaurants that accept card... you have to find them first of course.
Want to buy some cigarettes while you take a stroll in the evening? Good luck. Want a tuktuk to take you a mile across the beautifully walkable road infrastructure? Good luck. Want to get lunch with friends? Good luck.
90% of life doesn't exist inside the corpo "work hotel sleep" bubble, I described it to somebody as akin to trying to pay with bank transfer in the UK, technically you can do it... the manager will come out and spend 20 mins futzing, taxi drivers may be able to do it if you ask nicely, your shopping options will be very limited and far between because you're trying to transact in the non-predominant medium.
Yes, loads of places accept card, larger stores accept card, want coffee? Blue Tokai accepts card. Want Blinkit or Zomato? You need an Indian number first. Want a Hotel? Booking.com is predominantly "pay at the hotel" across most of India, which means it's a dice roll as to whether they'll accept card. You'd be surprised at how many hotels completely forget that not all customers are Indian+Aadhaar+UPI, except by the time you've got there and realized they accept neither C-form nor Card despite telling you explicitly they do - you've already spent the time, money and effort getting there only to find out that no... it's not practical in reality for you to book a hotel and pay for whatever reason. Repeat ad-nauseum everywhere daily