I see tons of reasons to have multiple currency IBAN’s. :) Especially for business use, but for personal use as well. It’d be nice if Bunq gets them, but I don’t expect they will create them. Shame, would actually be quite the opportunity to work together more with TransferWise so you can, for example, buy USD for your USD-acccount instantly; or convert a part of your USD-account back to EUR.
There’s loads of potential and convenience in multi-currency IBAN’s.