Part of the motivation is that even cash isn't accepted by everyone. Someone I was with last time I went had to get a stranger to make the UPI payment to vendor in exchange for cash. Nice of them, but what a faff, and my own Hindi wouldn't have been up to it. (Maybe you'd find someone willing and with enough English to arrange it, but that's only adding complexity.)

I'd definitely prefer this next time, if I could count on being able to set it up. (Or knew I'd go again so set it up while there for next time.)