Why modern sailing warships still carry engines

What was the last sail-only ship in naval service?

No last example is identified; modern naval sailing ships generally retain auxiliary machinery even when they make long voyages under sail.

Amerigo Vespucci still carries auxiliary diesel machinery despite making long passages under sail. A participant recalls her captain's frustration at having to use the diesel for a Thames arrival after sailing from Italy to Britain. Auxiliary machinery provides useful control even when a ship normally sails. Mixed machinery also appears in modern warships, with the Queen Elizabeth-class carriers using both gas turbines and diesels. Auxiliary electrical power and auxiliary propulsion are separate capabilities, so the presence of one does not establish the other.