The Damsel in Distress concept goes back to well before comics, going back to ancient Literature. It was a common plot device in 1800's dime novels and in early movies, so when newspaper comic strips came out it was a natural thing to use it there too and likewise when comics started being published as magazines.
Some cover artists turn the concept on it's head by having a male character be the "damsel" and a female character or another male character is coming to the "Damsel's" aid.
Some cover art portrays the Damsel without any apparent rescuer on the scene. In such cases we can only assume that she will have to get herself out of her predicament or she's done for. Additionally, the Damsel in Distress concept is often portrayed with the Damsel being held in restraints such as rope, chains or clamps, thus making these covers also part of the Bondage Cover concept.