The best instant payment system is cash. It allows the merchant to skip the taxes too. Unbeatable.
Brazilians also generally don't like to walk with cash in their pockets. Only politicians usually do it, but in their underpants.
The pros is that cash is analog, no battery, internet connection or digital system needed to process it.
Not that Pix isn't a risk, being forced to do bank transactions at gunpoint is a thing now, but anyway.
You still can buy airline tickets with cash. Not online though.