Another example, I was on holiday and prior to my trip I rented a car using my bunq card. during online payment I specifically said to take it from my main account.
whilst arriving to pickup the car I had to pay a gas fee which be returned upon giving the car back with full gas. Also this payment was done through my main sub-account. When the payment however got returned, it did not return to my main sub-account but to my transportation sub-account. Having a country sub-account would simply put all in one spot.