Why is it alive?

I have recently learned that the fleshling who caused a sucking response is stunted in the head. This makes sense, it’s only natural to have automatic negative feelings towards the deformed, however this raises a good question. I ponder now why the stunted one was allowed to live? All animals spare their defective offspring the suffering of an unsuccessful life, for what is the purpose of your offspring will be sure to fail. It seems that the humanoid fleshlings don’t follow this practice for some reason, perhaps he was correct but later damaged, or there is some purpose to having them around I cannot comprehend. Perhaps fleshlings value individual life over furthering their species, but that would be ridiculous. There must be some other reason. For now however I will avoid killing my herd when crippled beyond repair, they might prefer the suffering.