The goal was not just to satiate their lust, although that was also a big part of it. The goal was for them to have cubs. Not just cubs, but strong ones. The Alpha at that time had decided that it was the best way to increase their strength. So they'd take a little girl (usually the offspring of one of the enslaved women and a man of a higher bloodline) of a higher bloodline and let all of the men in their pack of equal or higher bloodline take turns with her. Whenever she got pregnant, she'd have that time away from the men to safely deliver the baby, and then the process would start all over again.