I think the roleplaying side of the scoundrel appeals to a lot of gamers, myself included.
The rogue has evolved in both CRPGs and tabletop to encompass a light armor wearing fighter who uses speed, deftness, cunning, and acrobatics to win out. In contrast the classical fighter is associated with strength, big weapons, and heavy armor. In essence both are actually different styles of fighter or martial warrior.
This is quite different from the Tolkien-esk Bilbo 'thief' with stealth and little combat ability that was the basis of the OD&D thief.