I was browsing through FireLemming's TLKFAA gallery, and part of her comic 'Shadows' really appealed to me- the idea that Scar let the cubs live, but used them to manipulate the lionesses.

In this imagined-up scene, Sarabi and the others are demanding to know why they should hunt for the hyenas when they're perfectly capable of getting their own food. Scar replies by saying:

"Well now, I don't think you fully understand the important role the hyenas play in our harmonious relationship. We lions provide them with food, and in return while we are out hunting, they make sure our darling cubs don't go missing. It is, after all, a big, bad world out there, and someone, like, say, young Chumvi here, might get hurt without their... protection."