That is incredibly useful for developing countries and the ecosystem of p2p allow in and out to fiat in a relatively smooth way
If you have a good non authoritarian government stable coins can be used to rollout a payment solution cheaply that works in any place an internet exist that could save you tons of money
You can use cryptocurrencies to get around currency restriction or failing currency which is mostly political problem and you use the crypto networks to help you in that
This is one of the weakest arguments in favour of crypto as it is not like you can't work with the current systems.
crypto currency network replaces swift which is a more cumbersome system with higher price and delay of days to send money between countries