While “cash” and ATM machines are the initial thought of vacationers/travelers, this leaves out a large part of why you would want a foreign currency account if you spend substantial time there:
Specially in Germany, paperless “ACH-style” bank transfers (“Ueberweisung” und “Lastschrift”) are used almost exclusively for all kind of personal and business payments, e.g., tuition, rent, utilities, cable/phone/Internet, car insurance, doctor bills, municipal fees - even online shopping. That’s how you pay any invoices!
Basically anything you would still write/mail a good-old paper-cheque for in the States (haven’t written/received a cheque in Germany in at least 30 years).
And, people will need your IBAN to send you money, whether is salaries, refunds, etc. - or whatever non-cash Euros you might need to receive from third parties.
So the benefit of having a Euro account is, that you can live/pay like the locals, rather than scrambling to figure out if they may or may not accept VISA/MC.
And the benefit of using a Euro debit card is, that you load it up with a balance from your U.S. checking account, at whatever “bulk” exchange rate at a timing you choose, and then you’ll be paying in Euro. Rather than having the U.S. credit card company use whatever daily ad-hoc exchange rate to charge your USD account for every single coffee you order.