In World War Two the German raider Kormoran sank HMAS Sydney, a light Cruiser.
And was sank in return, something which a privateer operating under a letter of marque doesn't want to happen.
The
Sydney/Kormoran story is both extremely odd and one we still know very little about despite
Sydney's wreck being discovered. Most of
Kormoran's crew survived and none at all from
Sydney. For decades, the accounts of the battle told by
Kormoran's surviving crew were generally discounted mostly because those accounts reflected rather poorly on
Sydney's crew. When the discovery of the wreck confirmed the
Kormoran's claims regarding the damage she caused to the light cruiser, the rest of her story has been reexamined.
There's a fairly exhaustive report on the 'net detailing the damage of the wreck and laying out what the investigators feel is the most plausible series of events aboard the cruiser leading up to and during the battle.
Anyway, seeing as a privateer wants to seize enemy ships and their cargoes in order to make a profit, merely sinking them isn't an option. Also, as others have already pointed out, advances in technology, especially radio, make attacking ships, let alone capturing them, very hazardous to the raider. This is perhaps the biggest reason why commerce raiding from the late 1800s onward evolved from "capturing by attack and/or threats" to "destroying by ambush".