Here is my coffee hypotesis:

The year is 2053. Dollar and Euros are long gone, so are the so-called "central bank cryptoassets",  that's because a system based on trust is no longer an option, people want only something that have value. Bitcoin, gold, even bullets and cigarettes are commonly used and daily traded for goods.

In that very probable scenario I enter in a bar and order a coffee using bitcoin. A coffee is worth way less than a Satoshi, so the barman hold me half a sovereign of gold and  a cigarette as rest.

This is simply not feasible if we don't implement a working ln so we have to hurry up